Method and apparatus for configuring dm-rs for v2x

ABSTRACT

A method includes generating a first DM-RS for V2X communication and a second DM-RS for V2X communication, the first DM-RS for V2X communication being mapped in a first symbol in a first slot of a subframe, the second DM-RS for V2X communication being mapped in a second symbol in the first slot; generating a third DM-RS for V2X communication and a fourth DM-RS for V2X communication, the third DM-RS for V2X communication being mapped in a first symbol in a second slot of the subframe, the fourth DM-RS for V2X communication being mapped in a second symbol in the second slot; and transmitting the first DM-RS for V2X communication, the second DM-RS for V2X communication, the third DM-RS for V2X communication, and the fourth DM-RS for V2X communication. The first DM-RS is generated based on a first group-hopping, and the second DM-RS is generated based on a second group-hopping.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/039,973, filed on Jul. 19, 2018, which is a continuation of U.S.patent application Ser. No. 15/275,169, filed on Sep. 23, 2016, whichclaims priority from and the benefit of Korean Patent Application Nos.10-2015-0136017, filed on Sep. 25, 2015, 10-2016-0058976, filed on May13, 2016, and 10-2016-0103277, filed on Aug. 12, 2016, which are herebyincorporated by reference in its entirety.

BACKGROUND 1. Field

The present disclosure relates to a wireless communication system, andmore particularly, to a method and apparatus for configuring ademodulation reference signal (DM-RS) for vehicle-to-X (V2X).

2. Discussion of the Background

Vehicle-to-everything (V2X, Vehicle-to-X) communication refers to acommunication scheme that exchanges or shares information associatedwith traffic conditions through communication with roadwayinfrastructures and other vehicles during driving. V2X may includevehicle-to-vehicle (V2V) indicating communication between vehicles,vehicle-to-pedestrian (V2P) indicating communication between terminalscarried by a vehicle and a person, and vehicle-to-infrastructure/network(V2I/N) indicating communication between a roadside unit (RSU) and anetwork. In this instance, the road side unit (RSU) may be a basestation or a transportation infrastructure entity embodied by a fixedterminal. For example, it may be an entity that transmits a speednotification to a vehicle.

V2X communication may be embodied based on a device-to-device (D2D)communication scheme. For example, control information, such as,scheduling assignment (SA) needs to be transmitted/received for V2Xcommunication, and data may be transmitted/received based on the controlinformation. Also, using a demodulation reference signal (DM-RS) isunder discussion so that a side that receives an SA and/or dataaccurately estimates a channel and demodulates the SA and/or data basedon the estimated channel. However, a method of generating a DM-RSsequence, which prevents an increase in DM-RS overhead in a subframe,and minimizes interference between neighbor terminals, has not beenprovided.

SUMMARY

Exemplary embodiments provide an apparatus and a method for configuringa demodulation reference signal (DM-RS) for vehicle-to-X (V2X).

One or more exemplary embodiments provide a method for transmittingDemodulation-Reference Signal (DM-RS) configured forVehicle-to-everything (V2X) communication. The method includesgenerating a first DM-RS for V2X communication and a second DM-RS forV2X communication, the first DM-RS for V2X communication being mapped ina first symbol in a first slot of a subframe, the second DM-RS for V2Xcommunication being mapped in a second symbol in the first slot of thesubframe; generating a third DM-RS for V2X communication and a fourthDM-RS for V2X communication, the third DM-RS for V2X communication beingmapped in a first symbol in a second slot of the subframe, the fourthDM-RS for V2X communication being mapped in a second symbol in thesecond slot of the subframe; and transmitting the first DM-RS for V2Xcommunication, the second DM-RS for V2X communication, the third DM-RSfor V2X communication, and the fourth DM-RS for V2X communication. Thefirst DM-RS for V2X communication is generated based on a firstgroup-hopping, and the second DM-RS for V2X communication is generatedbased on a second group-hopping.

One or more exemplary embodiments provide a method for transmittingDemodulation-Reference Signal (DM-RS) for Vehicle-to-everything (V2X)communication. The method includes generating a first DM-RS for V2Xcommunication and a second DM-RS for V2X communication, the first DM-RSfor V2X communication being mapped in a first symbol in a first slot ofa subframe, the second DM-RS for V2X communication being mapped in asecond symbol in the first slot of the subframe; generating a thirdDM-RS for V2X communication and a fourth DM-RS for V2X communication,the third DM-RS for V2X communication being mapped in a first symbol ina second slot of the subframe, the fourth DM-RS for V2X communicationbeing mapped in a second symbol in the second slot of the subframe; andtransmitting the first DM-RS for V2X communication, the second DM-RS forV2X communication, the third DM-RS for V2X communication, and the fourthDM-RS for V2X communication. Each of the first slot and the second slotconsists of seven symbols, respectively. The first slot precedes thesecond slot in a time axis. The first symbol in the first slot is symbol#2 and the second symbol in the first slot is symbol #5 if the sevensymbols in the first slot are arranged from symbol #0 to symbol #6, andthe first symbol in the second slot is symbol #1 and the second symbolin the second slot is symbol #4 if the seven symbols in the second slotare arranged from symbol #0 to symbol #6.

One or more exemplary embodiments provide a method for transmittingDemodulation-Reference Signal (DM-RS) configured forVehicle-to-everything (V2X) communication. The method includesgenerating a first DM-RS for V2X communication and a second DM-RS forV2X communication, the first DM-RS for V2X communication being mapped ina first symbol in a first slot of a subframe, the second DM-RS for V2Xcommunication being mapped in a second symbol in the first slot of thesubframe; generating a third DM-RS for V2X communication and a fourthDM-RS for V2X communication, the third DM-RS for V2X communication beingmapped in a first symbol in a second slot of the subframe, the fourthDM-RS for V2X communication being mapped in a second symbol in thesecond slot of the subframe; applying first orthogonal sequence [+1 +1+1 +1] or second orthogonal sequence [+1 −1 +1 −1] in association withthe first, second, third, and fourth DM-RSs for V2X communication; andtransmitting the first DM-RS for V2X communication, the second DM-RS forV2X communication, the third DM-RS for V2X communication, and the fourthDM-RS for V2X communication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, FIG. 2, and FIG. 3 are diagrams illustrating a V2X scenarioassociated with the present disclosure.

FIG. 4 illustrates an example of an uplink (UL) DM-RS in a UL channeland a DM-RS in a sidelink (SL) channel for D2D (or ProSe).

FIG. 5 illustrates an example of a DM-RS in a channel for PC5 link-basedV2X that complies with D2D (or ProSe) of the present disclosure.

FIG. 6 is a block diagram illustrating a wireless communication systemwhere embodiments of the present disclosure are implemented.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Exemplary embodiments of the present invention will be described morefully hereinafter with reference to the accompanying drawings, in whichexemplary embodiments of the invention are shown. Throughout thedrawings and the detailed description, unless otherwise described, thesame drawing reference numerals are understood to refer to the sameelements, features, and structures. In describing the exemplaryembodiments, detailed description on known configurations or functionsmay be omitted for clarity and conciseness.

Further, the description described herein is related to a wirelesscommunication network, and an operation performed in a wirelesscommunication network may be performed in a process of controlling anetwork and transmitting data by a system that controls a wirelessnetwork, e.g., a base station, or may be performed in a user equipmentconnected to the wireless communication network.

That is, it is apparent that various operations, which are performed forcommunicating with a terminal in a network formed of a plurality ofnetwork nodes including a base station (BS), are executable by the BS orother network nodes excluding the BS. The ‘BS’ may be replaced with theterms, such as, a fixed station, a Node B, an eNode B (eNB), an accesspoint (AP), and the like. Also, the ‘terminal’ may be replaced with theterms, such as a User Equipment (UE), a Mobile Station (MS), a MobileSubscriber Station (MSS), a Subscriber Station (SS), a non-AP station(non-AP STA), and the like.

The terms used as abbreviations in the present disclosure are defined asfollows.

D2D: Device to Device (communication)

ProSe: (Device to Device) Proximity Services

SL: Sidelink

SCI: Sidelink Control Information

PSSCH: Physical Sidelink Shared Channel

PSBCH: Physical Sidelink Broadcast Channel

PSCCH: Physical Sidelink Control Channel

PSDCH: Physical Sidelink Discovery Channel

SLSS: Sidelink Synchronization Signal (=D2DSS (D2D SynchronizationSignal))

SA: Scheduling assignment

DM-RS: DeModulation Reference Signal

PSSID: Physical-layer Sidelink Synchronization Identity

nSAID: Sidelink group destination identity

nSLID: Physical layer sidelink synchronization identity

PUSCH: Physical Uplink Shared Channel

Also, various operation modes may be defined based on a resourceallocation scheme for a direct link (e.g., D2D, ProSe, or SLcommunication). When data and control information for a direct link(e.g., D2D, ProSe, or SL communication) are indicated as direct data anddirect control information, respectively, mode 1 indicates an operationmode in which a base station (or a relay station) accurately schedules aresource that a terminal uses to transmit direct data and direct controlinformation, and mode 2 indicates an operation mode in which a terminalautonomously selects a resource from a resource pool to transmit directdata and direct control information.

Hereinafter, although embodiments of the present disclosure aredescribed by using V2X communication as an example, the scope of thepresent disclosure may not be limited to V2X communication. Further, theembodiments of the present disclosure may be applied to direct linkbased communication, such as D2D, ProSe, SL communication, or the like.

V2X is a term that generally indicates V2V, V2P, and V2I/N, and each ofV2V, V2P, and V2I/N may be defined as shown in Table 1, in associationwith LTE communication.

TABLE 1 V2V covering LTE-based communication between vehicles V2Pcovering LTE-based communication between a vehicle and a device carriedby an individual (e.g. handheld terminal carried by a pedestrian,cyclist, driver or passenger) V2I/N covering LTE-based communicationbetween a vehicle and a roadside unit/network A roadside unit (RSU) is astationary infrastructure entity supporting V2X applications that canexchange messages with other entities supporting V2X applications. Note:RSU is a term frequently used in existing ITS specifications, and thereason for introducing the term in the 3GPP specifications is to makethe documents easier to read for the ITS industry. RSU is a logicalentity that combines V2X application logic with the functionality of aneNB (referred to as eNB-type RSU) or UE (referred to as UE-type RSU).

For a V2V operation based on PC5 which is a D2D communication link (thatis, a direct interface between two devices that support ProSe) out ofV2X, various scenarios such as Table 2, Table 3, and Table 4 areconsidered with reference to FIGS. 1, 2, and 3.

FIG. 1, FIG. 2, and FIG. 3 are diagrams illustrating a V2X scenarioassociated with the present disclosure.

Table 2 and FIG. 1 illustrate a scenario that supports a V2X operationthat is based on only a PC5 interface. Part (a) of FIG. 1 illustrates aV2V operation, part (b) of FIG. 1 illustrates a V2I operation, and part(c) of FIG. 1 illustrates a V2P operation.

TABLE 2 This scenario supports V2X operation only based on PC5. In thisscenario, a UE transmits a V2X message to multiple UEs at a local areain sidelink. For V2I, either transmitter UE or receiver UE(s) areUE-type RSU. For V2P, either transmitter UE or receiver UE(s) arepedestrian UE.

Table 3 and FIG. 2 illustrate a scenario that supports a V2X operationthat is based on only a Uu interface (that is, an interface between a UEand an eNB). Part (a) of FIG. 2 illustrates a V2V operation, part (b) ofFIG. 2 illustrates a V2I operation, and part (c) of FIG. 2 illustrates aV2P operation.

TABLE 3 This scenario supports V2X operation only based on Uu. In thisscenario, For V2V and V2P, a UE transmits a V2X message to E-UTRAN inuplink and E-UTRAN transmits it to multiple UEs at a local area indownlink. For V2I, when receiver is eNB type RSU, a UE transmits a V2Imessage to E-UTRAN(eNB type RSU) in uplink; when transmitter is eNB typeRSU, E-UTRAN(eNB type RSU) transmits a I2V message to multiple UEs at alocal area in downlink. For V2P, either transmitter UE or receiver UE(s)are pedestrian UE. To support this scenario, E-UTRAN performs uplinkreception and downlink transmission of V2X messages. For downlink,E-UTRAN may use a broadcast mechanism.

Table 4 and FIG. 3 illustrate a scenario that supports a V2X operationthat uses both a Uu interface and a PC5 interface. Part (a) of FIG. 3illustrates scenario 3A of Table 4 and part (b) of FIG. 3 illustratesscenario 3B of Table 4.

TABLE 4 This scenario supports V2V operation using both Uu and PC5.Scenario In this scenario, a UE transmits a V2X message to other UEs 3Ain sidelink. One of the receiving UEs is a UE type RSU which receivesthe V2X message in sidelink and transmits it to E-UTRAN in uplink.E-UTRAN receives the V2X message from the UE type RSU and then transmitsit to multiple UEs at a local area in downlink. To support thisscenario, E-UTRAN performs uplink reception and downlink transmission ofV2X messages. For downlink, E-UTRAN may use a broadcast mechanism.Scenario In this scenario, a UE transmits a V2X message to E- 3B UTRANin uplink and E-UTRAN transmits it to one or more UE type RSUs. Then,the UE type RSU transmits the V2X message to other UEs in sidelink. Tosupport this scenario, E-UTRAN performs uplink reception and downlinktransmission of V2X messages. For downlink, E-UTRAN may use a broadcastmechanism.

Hereinafter, a UL DM-RS for a UL PUSCH will be described.

Basic information associated with a UL DM-RS in a UL PUSCH is defined asshown in Table 5, provided below.

Hereinafter, a DM-RS (hereinafter, an SL DM-RS) for an SLPSSCH/PSCCH/PSDCH/PSBCH will be described.

Basic information associated with an SL DM-RS for D2D (or ProSe) is asfollows. Unlike the UL DM-RS for the UL PUSCH which has been describedwith reference to Table 5, the definitions of predetermined parametersand applied equations may be changed for the SL DM-RS as shown in Table6 and Table 7.

TABLE 6 Parameter PSSCH PSCCH Group hopping enabled disabled n_(ID)^(RS) n_(ID) ^(SA) — n_(s) n_(ss) ^(PSSCH) — f_(ss) n_(ID) ^(SA) mod30 0Sequence hopping disabled disabled Cyclic shift n_(cs,λ) └n_(ID)^(SA)/2┘mod8 0 Orthogonal [w^(λ)(0) w^(λ)(1)] [+1 +1] if n_(ID) ^(SA)mod 2 = 0 [+1 +1] sequence [+1 −1] if n_(ID) ^(SA) mod 2 = 1 Referencesignal M_(sc) ^(RS) M_(sc) ^(PSSCH) M_(sc) ^(PSCCH) length Number oflayers υ 1 1 Number of antenna P 1 1 ports

TABLE 7 Parameter PSDCH PSBCH Group disabled disabled hopping f_(ss) 0└N_(ID) ^(SL)/16┘mod30 Sequence disabled disabled hopping Cyclic shiftn_(cs,λ) 0 └N_(ID) ^(SL)/2┘mod8 Orthogonal [w^(λ)(0) w^(λ)(1)] [+1 +1][+1 +1] if N_(ID) ^(SL) mod 2 = 0 sequence [+1 −1] if N_(ID) ^(SL) mod 2= 1 Reference M_(sc) ^(RS) M_(sc) ^(PSDCH) M_(sc) ^(PSBCH) signal lengthNumber of υ 1 1 layers Number of P 1 1 antenna ports

Hereinafter, embodiments of the present disclosure will be described indetail.

In the case of a UL DM-RS in a UL PUSCH and a DM-RS in a slidelink (SL)PSSCH/PSCCH/PSDCH/PSBCH for LTE-based D2D (ProSe), a DM-RS is generatedby mapping a DM-RS sequence to a single symbol for each slot as shown inFIG. 4 and the DM-RS is transmitted. That is, a single subframe includestwo slots (that is, a slot having an even number index (that is, an evenslot)) and a slot having an odd number index (that is, an odd slot)),and a single slot may include 6 or 7 symbols based on the length of acyclic prefix (CP). For example, in the case of a normal CP, 7 symbols(that is, symbol indices #0, #1, . . . , #6) are included in a singleslot, and a DM-RS may be mapped to a fourth symbol (that is, a symbolindex #3) out of the symbols. In the case of an extended CP, 6 symbols(that is, symbol indices #0, #1, . . . , #5) are included in a singleslot, and a DM-RS may be mapped to a third symbol (that is, a symbolindex #2) out of the symbols.

However, in the case of V2X, a DM-RS may be mapped using a larger numberof symbols, when compared to the example of FIG. 4, in a single subframeas shown in FIG. 5, by taking into consideration high Doppler effect.

In a V2X communication, relatively higher Doppler effect may occur dueto the moving speed of the vehicle performing the V2X communication. Inorder to address such a problem, more symbols may be used to map DM-RSfor a V2X communication in a subframe. Further, if the same sequencegeneration method for V2X DM-RS is used as utilized in LTE PUSCH DM-RSor D2D DM-RS generations, e.g., using the same group-hopping, cyclicshift, and orthogonal sequence, interference among DM-RSs for V2Xtransmitted from various devices may increase. The increased symbols ina subframe for DM-RS mapping may also exacerbate the interferenceproblem.

One or more exemplary embodiments illustrated herein address theproblems by utilizing more efficient group-hopping, cyclic shiftselection, and orthogonal sequence selection for V2X DM-RS generations.One or more exemplary embodiments also reduces the possibleinterferences among DM-RSs for V2X communication transmitted fromvarious devices, and improves the communication quality in channelmeasurements for demodulating control information and data throughDM-RSs for V2X communication.

Part (a) of FIG. 5 illustrates that a DM-RS is transmitted through afourth symbol (symbol #3) and a sixth symbol (symbol #5) of each slot,in the case of the normal CP. However, this is merely an example, andtwo symbols randomly selected out of a total of 7 symbols included in asingle slot may be determined as symbols through which a DM-RS istransmitted. For example, one of the two symbols through which a DM-RSis transmitted in each slot is a fourth symbol (symbol #3) of each slot,and the other symbol may be one of a first symbol (symbol #0), a secondsymbol (symbol #1), a third symbol (symbol #2), a fifth symbol (symbol#4), a sixth symbol (symbol #5), and a seventh symbol (symbol #6).

In the same manner, the part (a) of FIG. 5 illustrates that a DM-RS istransmitted through a third symbol (symbol #2) and a fifth symbol(symbol #4) of each slot, in the case of the extended CP. However, thisis merely an example, and two symbols randomly selected out of a totalof 6 symbols included in a single slot may be determined as symbolsthrough which a DM-RS is transmitted. For example, one of the twosymbols through which a DM-RS is transmitted in each slot is a thirdsymbol (symbol #2) of each slot, and the other symbol may be one of afirst symbol (symbol #0), a second symbol (symbol #1), a fourth symbol(symbol #3), and a fifth symbol (symbol #4), a sixth symbol (symbol #5).

In part (b) of FIG. 5, in the case of the normal CP, two symbols out ofseven symbols in each of a first slot and a second slot may bedetermined as symbols through which a DM-RS is transmitted. For example,as illustrated in the part (b) of FIG. 5, two symbols through which aDM-RS is transmitted out of seven symbols in the first slot may be athird symbol (symbol #2) and a sixth symbol (symbol #5). Two symbolsthrough which a DM-RS is transmitted out of seven symbols in the secondslot may be a second symbol (symbol #1) and a fifth symbol (symbol #4).

In the same manner, in FIG. the part (b) of 5, in the case of theextended CP, two symbols out of six symbols in each of a first slot anda second slot may be determined as symbols through which a DM-RS istransmitted. For example, as illustrated in the part (b) of FIG. 5, twosymbols through which a DM-RS is transmitted out of six symbols in thefirst slot may be a second symbol (symbol #1) and a fifth symbol (symbol#4). Two symbols through which a DM-RS is transmitted out of six symbolsin the second slot may be a second symbol (symbol #1) and a fifth symbol(symbol #4).

In part (c) of FIG. 5, in the case of the normal CP, three symbols outof 14 symbols in a single subframe that includes a first slot and asecond slot may be determined as symbols through which a DM-RS istransmitted. For example, as illustrated in the part (c) of FIG. 5,three symbols through which a DM-RS is transmitted out of 14 symbolsincluded in the single subframe may be a fourth symbol (symbol #3) and aseventh symbol (symbol #6) in the first slot, and a fourth symbol(symbol #3) in the second slot.

In the same manner, in the part (c) of FIG. 5, in the case of theextended CP, three symbols out of 12 symbols in a single subframe thatincludes a first slot and a second slot may be determined as symbolsthrough which a DM-RS is transmitted. For example, as illustrated in thepart (c) of FIG. 5, three symbols through which a DM-RS is transmittedout of 12 symbols included in the single subframe may be a fourth symbol(symbol #3) and a sixth symbol (symbol #5) in the first slot, and asecond symbol (symbol #1) in the second slot.

In this instance, to minimize interference from neighbor terminals, aneffective group hopping method, a cyclic shift method, an orthogonalcover code (OCC) or orthogonal sequence mapping method, or the like needto be considered when a DM-RS is generated.

Hereinafter, group hopping for the present disclosure will be described.

In the case of D2D (ProSe), group hopping may be applied for each slotwhen a DM-RS that links with a PSSCH and a PSCCH is transmitted, asshown in Equation 1 below.

                                     [Equation  1]${f_{gh}\left( n_{s} \right)} = \left\{ \begin{matrix}0 & {{if}\mspace{14mu} {group}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {disabled}} \\{\left( {\sum_{i = 0}^{7}{{c\left( {{8n_{s}} + i} \right)} \cdot 2^{i}}} \right){mod}\; 30} & {{if}\mspace{14mu} {group}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {enabled}}\end{matrix} \right.$

In Equation 1, n_(s) denotes a slot index. Also, c(i) denotes apseudo-random sequence that is defined as Gold sequence having a degreeof 31, and a pseudo-random sequence generator for the pseudo-randomsequence is initialized to

$c_{init} = \left\lfloor \frac{n_{ID}^{SA}}{30} \right\rfloor$

at the beginning of each radio frame. Here, n^(RS) _(ID) may be N^(cell)_(ID) which is a physical cell ID (PCID), or n^(PUCCH) _(ID) orn^(PUSCH) _(ID) which is a parameter indicated by an RRC or a higherlayer signaling.

Group hopping of Equation 1 is appropriate for the case in which a DM-RSis transmitted through a single symbol for each slot. However, by takinginto consideration the case in which a DM-RS is transmitted through aplurality of symbols of each slot in V2X, there is a desire for a moreeffective group hopping method, and the present disclosure proposes thefollowing method.

Hereinafter, method 1 will be defined for new group hopping according tothe present disclosure.

According to method 1, as shown in Equation 2 below, by taking intoconsideration the case in which a DM-RS is generated in two symbols in asingle slot which corresponds to the example of the part (a) of FIG. 5or the part (b) of FIG. 5, two different group hopping patterns aredefined in each slot, irrespective of the locations of the two symbols.One group hopping pattern is applied to a first symbol through which aDM-RS is transmitted in the slot, and the other group hopping pattern isapplied to a second symbol through which the DM-RS is transmitted in theslot. In this instance, l′=0 or 1.

                                     [Equation  2]$f_{gh} = \left\{ \begin{matrix}0 & {{if}\mspace{14mu} {group}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {disabled}} \\{\left( {\sum_{i = 0}^{7}{{c\left( {{16n_{ss}^{PSSCH}} + {8l^{\prime}} + i} \right)} \cdot 2^{i}}} \right){mod}\; 30} & {{if}\mspace{14mu} {group}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {enabled}}\end{matrix} \right.$

Here, c(i) denotes a pseudo-random sequence that is defined as Goldsequence having a degree of 31, and a pseudo-random sequence generatorfor the pseudo-random sequence is initialized to

$c_{init} = \left\lfloor \frac{n_{ID}^{SA}}{30} \right\rfloor$

at the beginning of each slot that satisfies n^(PSSCH) _(ss)=0. In thisinstance, n^(PSSCH) _(ss) denotes a current slot number in the subframepool for a sidelink. Here, n^(SA) _(ID) may be a sidelink groupdestination identity.

Hereinafter, method 2 will be defined for new group hopping according tothe present disclosure.

According to method 2, as shown in Equation 3 below, by taking intoconsideration the case in which a DM-RS is generated in three symbols ina single subframe which corresponds to the part (c) of FIG. 5, threedifferent group hopping patterns are defined in each subframe,irrespective of the locations of the three symbols. A first grouphopping pattern is applied to a first symbol through which a DM-RS istransmitted in the subframe, a second group hopping pattern is appliedto a second symbol through which the DM-RS is transmitted in thesubframe, and a third group hopping pattern is applied to a third symbolthrough which the DM-RS is transmitted in the subframe. In thisinstance, l′=0, 1, or 2.

                                 [Equation  3]$f_{gh} = \left\{ \begin{matrix}0 & {{if}\mspace{14mu} {group}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {disabled}} \\{\left( {\sum_{i = 0}^{7}{{c\left( {{8l^{\prime}} + i} \right)} \cdot 2^{i}}} \right){mod}\; 30} & {{if}\mspace{14mu} {group}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {enabled}}\end{matrix} \right.$

Here, c(i) denotes a pseudo-random sequence that is defined as Goldsequence having a degree of 31, and a pseudo-random sequence generatorfor the pseudo-random sequence is initialized to

$c_{init} = {{\left\lfloor \frac{N_{ID}^{SL}}{30} \right\rfloor \mspace{14mu} {or}\mspace{14mu} c_{init}} = \left\lfloor \frac{\left\lfloor {N_{ID}^{SL}\text{/}24} \right\rfloor}{30} \right\rfloor}$

at the beginning of each PSBCH subframe (a subframe that transmits aPSBCH). Here, N^(SL) _(ID) may be a physical layer sidelinksynchronization identity.

Hereinafter, method 3 will be defined for new group hopping according tothe present disclosure.

Method 3 defines a different group hopping pattern for each of thesymbols in a single slot, and a corresponding symbol through which aDM-RS is transmitted applies a corresponding group hopping pattern ofthe symbol, as shown in Equation 4 below. This is applied to all of thecases illustrated through FIGS. 5A, 5B, and 5C. In this instance, N^(SL)_(symb) denotes the number of symbols in a single slot in a sidelink(SL) (7 in the case of a normal CP, and 6 in the case of an extendedCP), and l=0, 1, . . . , N^(SL) _(symb) denotes a symbol index in asingle slot.

                                     [Equation  4]$f_{gh} = \left\{ \begin{matrix}0 & {{if}\mspace{14mu} {group}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {disabled}} \\{\left( {\sum_{i = 0}^{7}{{c\left( {{8 \cdot N_{symb}^{SL} \cdot n_{s}} + {8l} + i} \right)} \cdot 2^{i}}} \right){mod}\; 30} & {{if}\mspace{14mu} {group}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {enabled}}\end{matrix} \right.$

In Equation 4, n_(s) is n^(PSSCH) _(ss) when the equation is applied toa DM-RS for a PSSCH.

In Equation 4, n_(s) may have two types of values, that is, 0 or 1, whenthe equation is applied to a DM-RS for a PSBCH.

Also, c(i) denotes a pseudo-random sequence defined as Gold sequencehaving a degree of 31.

When Equation 4 is applied to the DM-RS for the PSSCH, the pseudo-randomsequence generator for the pseudo-random sequence may be initialized to

$c_{init} = \left\lfloor \frac{n_{ID}^{SA}}{30} \right\rfloor$

at the beginning of each slot that satisfies n^(PSSCH) _(ss)=0.

When Equation 4 is applied to the DM-RS for the PSCBCH, thepseudo-random sequence generator for the pseudo-random sequence may beinitialized to

$c_{init} = {{\left\lfloor \frac{N_{ID}^{SL}}{30} \right\rfloor \mspace{14mu} {or}\mspace{14mu} c_{init}} = \left\lfloor \frac{\left\lfloor {N_{ID}^{SL}\text{/}24} \right\rfloor}{30} \right\rfloor}$

at the beginning of every PSBCH subframe (a subframe that transmits aPSBCH).

In this instance, n^(PSSCH) _(ss) denotes a current slot number in thesubframe pool for a sidelink. Here, n^(SA) _(ID) is a sidelink groupdestination identity, and N^(SL) _(ID) is a physical layer sidelinksynchronization identity.

Method 1 and method 2 for new group hopping according to the presentdisclosure for V2X define group hopping by taking into considerationonly a symbol to which a DM-RS is mapped, in the same manner as LTEPUSCH-based D2D (ProSe).

Method 3 for new group hopping according to the present disclosure forV2X applies group hopping for each symbol, and a symbol to which a DM-RSis mapped applies a predetermined group hopping of the correspondingsymbol.

When method 3 for new group hopping according to the present disclosureis applied, group hopping for a symbol to which a DM-RS is mapped in theLTE PUSCH based-D2D (ProSe) and group hopping for a symbol to which aDM-RS is mapped in V2X are set to be different from each other, andthus, interference may be reduced that may occur between the DM-RS inD2D (ProSe) and the DM-RS in V2X, which may be transmitted in parallelin the same symbol having the same c_(init) (e.g., n^(SA) _(ID) isdifferent from each other but

$c_{init} = \left\lfloor \frac{n_{ID}^{SA}}{30} \right\rfloor$

is identical to each other), which is an advantage.

For example, in a symbol to which a DM-RS is mapped in a first slot inthe LTE PUSCH-based D2D (ProSe), group hopping is determined based on apseudo-random sequence value of c(0) to c(7). In this instance, whenmethod 1 and method 2 for new group hopping according to the presentdisclosure for V2X are applied, group hopping may be determined based ona pseudo-random sequence value of c(0) to c(7) in a first symbol of afirst slot to which a DM-RS is mapped (herein, this symbol may be asymbol located in the same location of a symbol to which a DM-RS ismapped in a first slot in the LTE PUSCH-based D2D (ProSe)). However,when method 3 for new group hopping according to the present disclosurefor V2X is applied, group hopping may be determined based on apseudo-random sequence value of c(8(symbol number)+0) to c(8(symbolnumber)+7) in a first symbol of a first slot to which a DM-RS is mapped(herein, this symbol may be a symbol located in the same location of asymbol to which a DM-RS is mapped in a first slot in the LTE PUSCH-basedD2D (ProSe)).

Hereinafter, an orthogonal sequence (OCC) and a cyclic shift accordingto the present disclosure will be described.

A cyclic shift and an orthogonal sequence (OCC) are taken intoconsideration to minimize interference from neighbor terminals when aDM-RS is generated. In the case of D2D (ProSe), a length 2 orthogonalcover code (OCC) is applied as the orthogonal sequence (OCC) by takinginto account the case in which a DM-RS is transmitted through twosymbols in a single subframe. However, in the case of V2X, a length 4orthogonal cover code (OCC) may be considered as an orthogonal sequence(OCC) by taking into account the case in which a DM-RS is transmittedthrough four symbols in a single subframe. Accordingly, an orthogonalsequence (OCC) needs to be changed to effectively minimize interferenceamong neighbor terminals. Also, application of an effective cyclic shiftalso needs to be considered along with changing the orthogonal sequence(OCC).

Here, when a DM-RS is transmitted through four symbols in the singlesubframe, the locations of two symbols out of the four symbols in thesubframe are the same as the locations of two symbols through which aDM-RS is transmitted in the single subframe in D2D (ProSe), and thelocations of the remaining two symbols are configured additionally. Thismethod may be effective from the perspective of the minimization ofinterference from a neighbor terminal.

In the case in which a terminal that transmits a DM-RS in theenvironment of V2X and a terminal that transmits a DM-RS in theenvironment of D2D (ProSe) coexist, when the application of anorthogonal sequence (OCC) for the transmission of a DM-RS in the V2Xenvironment is extended based on the application of an orthogonalsequence (OCC) for the transmission of a DM-RS in the D2D (ProSe),mutual interference may be alleviated through an orthogonal sequence(OCC). For example, when an orthogonal sequence (OCC) application schemefor two symbols out of four symbols in a single subframe when a DM-RS istransmitted in the V2X environment is the same as an orthogonal sequence(OCC) application scheme for two symbols in a single subframe when aDM-RS is transmitted in D2D (ProSe), mutual interference may bealleviated in the two symbols.

As described above, in the case of V2X, a method of transmitting a DM-RSthrough four symbols in a single subframe may be preferentiallyconsidered by taking into consideration high Doppler effect or the like.However, in the case of a PSBCH that transmits together with a sidelinksynchronization signal (SLSS) in a subframe, a method of transmitting aDM-RS through three symbols in a single subframe may be considered bytaking into account symbols for the SLSS. In this instance, a length 3orthogonal cover code (OCC) may be considered as an orthogonal sequence(OCC). Accordingly, an orthogonal sequence (OCC) may need to be changedto effectively minimize interference among neighbor terminals. Also, theapplication of an effective cyclic shift also needs to be consideredalong with changing the orthogonal sequence (OCC).

First, the case in which two types of OCCs are used like the D2D (ProSe)and the length of an OCC is 4 (method 1-1 and method 1-2 for anorthogonal sequence (OCC) and a cyclic shift) may be considered for V2X,whereas two length 2 OCCs are used in the case of D2D (ProSe). Althoughthis may be applied to the example illustrated in the part (a) of FIG.5, the present disclosure may not be limited thereto.

This will be described in details as follows.

[Method 1-1 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, one of two symbolsthrough which a DM-RS is transmitted in each slot is a fourth symbol(symbol #3) of each slot, in the same manner as a DM-RS that links withan existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe subsequent symbols (a fifth symbol (symbol #4), a sixth symbol(symbol #5), and a seventh symbol (symbol #6)) in the slot.

Also, this is the case in which an extended CP is used, one of twosymbols through which a DM-RS is transmitted in each slot is a thirdsymbol (symbol #2) of each slot, in the same manner as a DM-RS thatlinks with an existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe subsequent symbols (a fourth symbol (symbol #3), a fifth symbol(symbol #4), and a sixth symbol (symbol #5)) in the slot.

In this instance, this is the case in which the locations of two symbolsout of the four symbols in a single subframe are the same as thelocations of two symbols for D2D(ProSe) and the remaining two symbolsare added, and thus, V2X may always transmit a DM-RS through a total offour symbols in a single subframe by adding two symbols in addition totwo existing symbols in the single subframe. Alternatively, one out oftwo schemes may be selected and used, the schemes including a scheme(scheme #1) that transmits a DM-RS through two existing symbols in asingle subframe in the same manner as D2D (ProSe), through a higherlayer signaling such as RRC or the like, and a scheme (scheme #2) thattransmits a DM-RS through a total of four symbols by adding two symbolsin addition to the two existing symbols in the single subframe.

TABLE 8 Parameter PSSCH PSCCH Cyclic n_(cs,λ) └n_(ID) ^(SA)/2┘mod8 0shift Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1 +1 +1] ifn_(ID) ^(SA) mod 2 = 0 [+1 +1 +1 +1] sequence [+1 −1 −1 +1] if n_(ID)^(SA) mod 2 = 1 Parameter PSDCH PSBCH Cyclic n_(cs,λ) 0 └N_(ID)^(SL)/2┘mod8 shift Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1+1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 2 = 0 sequence [+1 −1 −1 +1]if N_(ID) ^(SL) mod2 = 1

As shown in Table 8, [+1 +1 +1 +1] and [+1 −1 −1 +1] may be used as twotypes of length 4 OCCs by taking into consideration the DM-RStransmission of a DM-RS that links with a PSSCH and a PSBCH through atotal of 4 symbols in a single subframe.

By taking into consideration the DM-RS transmission of a DM-RS thatlinks with a PSSCH and a PSBCH in D2D (ProSe) through a total of twosymbols in a single subframe, two types of length 2 OCCs, that is, [+1+1] and [+1 −1] may be used. This may be extended to [+1 +1 +1 +1] and[+1 −1 +1 −1] by taking into consideration the DM-RS transmissionthrough a total of four symbols in a single subframe. However, in thisinstance, OCC mapping in two symbols (a first symbol and a third symbolout of four symbols) of which the locations are the same as the existingD2D (ProSe), out of four symbols, may be changed, and thus, the OCCconfiguration as shown in Table 8 may be preferable.

Further, in association with a cyclic shift, the configuration that isthe same as the configuration in D2D (ProSe) may be possible.

[Method 1-2 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, one of two symbolsthrough which a DM-RS is transmitted in each slot is a fourth symbol(symbol #3) of each slot in the same manner as a DM-RS that links withan existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe previous symbols (a first symbol (symbol #0), a second symbol(symbol #1), and a third symbol (symbol #2)) in the slot.

Also, this is the case in which an extended CP is used, one of twosymbols through which a DM-RS is transmitted in each slot is a thirdsymbol (symbol #2) of each slot, in the same manner as a DM-RS thatlinks with an existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe previous symbols (a first symbol (symbol #0) and a second symbol(symbol #1)) in the slot.

In this instance, this is the case in which the locations of two symbolsout of the four symbols in a single subframe are the same as thelocations of two symbols for D2D(ProSe) and the remaining two symbolsare added, and thus, V2X may always transmit a DM-RS through a total offour symbols by adding two symbols in addition to two existing symbolsin the single subframe. Alternatively, one out of two schemes may beselected and used, the schemes including a scheme (scheme #1) thattransmits a DM-RS through two existing symbols in a single subframe inthe same manner as D2D (ProSe), through a higher layer signaling such asRRC or the like, and a scheme (scheme #2) that transmits a DM-RS througha total of four symbols by adding two symbols in addition to the twoexisting symbols in the single subframe.

TABLE 9 Parameter PSSCH PSCCH Cyclic n_(cs,λ) └n_(ID) ^(SA)/2┘mod8 0shift Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1 +1 +1] ifn_(ID) ^(SA) mod 2 = 0 [+1 +1 +1 +1] sequence [−1 +1 +1 −1] if n_(ID)^(SA) mod 2 = 1 Parameter PSDCH PSBCH Cyclic n_(cs,λ) 0 └N_(ID)^(SL)/2┘mod8 shift Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1+1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 2 = 0 sequence [−1 +1 +1 −1]if N_(ID) ^(SL) mod 2 = 1

As shown in Table 9, [+1 +1 +1 +1] and [−1 +1 +1 −1] may be used as twotypes of length 4 OCCs by taking into consideration the DM-RStransmission of a DM-RS that links with a PSSCH and a PSBCH through atotal of 4 symbols in a single subframe.

By taking into consideration the DM-RS transmission of a DM-RS thatlinks with a PSSCH and a PSBCH in D2D (ProSe) through a total of twosymbols in a single subframe, two types of length 2 OCCs, that is, [+1+1] and [+1 −1] may be used. This may be extended to [+1 +1 +1 +1] and[+1 −1 +1 −1] by taking into consideration the DM-RS transmissionthrough a total of four symbols in a single subframe. However, in thisinstance, OCC mapping in two symbols (a second symbol and a fourthsymbol out of four symbols) of which the locations are the same as theexisting D2D (ProSe), out of four symbols, may be changed, and thus, theOCC configuration as shown in Table 9 may be preferable.

Further, in association with a cyclic shift, the configuration that isthe same as the configuration in D2D (ProSe) may be possible.

Subsequently, the case in which the number of types of OCCs is extendedto 4 and the length of an OCC is 4 (method 2-1, method 2-2, method 3-1,and method 3-2 for an orthogonal sequence (OCC) and a cyclic shift) maybe considered for V2X, whereas two length 2 OCCs are used in the case ofD2D (ProSe). Although this may be applied to the example illustrated inthe part (a) of FIG. 5, the present disclosure may not be limitedthereto.

[Method 2-1 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, one of two symbolsthrough which a DM-RS is transmitted in each slot is a fourth symbol(symbol #3) of each slot, in the same manner as a DM-RS that links witha UL PUSCH or a DM-RS that links with a PSSCH/PSCCH/PDSCH/PSBCH inD2D(ProSe), and the other symbol is one of subsequent symbols (a fifthsymbol (symbol #4), a sixth symbol (symbol #5), and a seventh symbol(symbol #6)) in the slot.

Also, this is the case in which an extended CP is used, one of twosymbols through which a DM-RS is transmitted in each slot is a thirdsymbol (symbol #2) of each slot, in the same manner as a DM-RS thatlinks with an existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe subsequent symbols (a fourth symbol (symbol #3), a fifth symbol(symbol #4), and a sixth symbol (symbol #5)) in the slot.

In this instance, this is the case in which the locations of two symbolsout of the four symbols in a single subframe are the same as thelocations of two symbols for D2D(ProSe) and the remaining two symbolsare added, and thus, V2X may always transmit a DM-RS through a total offour symbols by adding two symbols in addition to two existing symbolsin the single subframe. Alternatively, one out of two schemes may beselected and used, the schemes including a scheme (scheme #1) thattransmits a DM-RS through two existing symbols in a single subframe inthe same manner as D2D (ProSe), through a higher layer signaling such asRRC or the like, and a scheme (scheme #2) that transmits a DM-RS througha total of four symbols by adding two symbols in addition to the twoexisting symbols in the single subframe.

TABLE 10 Parameter PSSCH PSCCH Cyclic shift n_(cs,λ) └n_(ID)^(SA)/2┘mod8 0 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1+1 +1] if n_(ID) ^(SA) mod 4 = 0 [+1 +1 +1 +1] sequence [+1 −1 −1 +1] ifn_(ID) ^(SA) mod 4 = 1 [+1 −1 +1 −1] if n_(ID) ^(SA) mod 4 = 2 [+1 +1 −1−1] if n_(ID) ^(SA) mod 4 = 3 Parameter PSDCH PSBCH Cyclic shiftn_(cs,λ) 0 └N_(ID) ^(SL)/2┘mod8 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)w^(λ)(3)] [+1 +1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 4 = 0 sequence[+1 −1 −1 +1] if N_(ID) ^(SL) mod 4 = 1 [+1 −1 +1 −1] if N_(ID) ^(SL)mod 4 = 2 [+1 +1 −1 −1] if N_(ID) ^(SL) mod 4 = 3

As shown in Table 10, [+1 +1 +1 +1], [+1 −1 −1 +1], [+1 −1 +1 −1], and[+1 +1 −1 −1] may be used as four types of length 4 OCCs by taking intoconsideration the DM-RS transmission of a DM-RS that links with a PSSCHand a PSBCH through a total of 4 symbols in a single subframe.

The four length 4 OCCs, that is, [+1 +1 +1 +1], [+1 −1 −1 +1], [+1 −1 +1−1], and [+1 +1 −1 −1] may be used respectively for the cases havingremainders of 0, 1, 2, and 3 that are obtained by dividing n^(SA) _(ID)by 4 in the case of a DM-RS that links with a PSSCH, and may be usedrespectively for the cases having remainders of 0, 1, 2, and 3 that areobtained by dividing n^(SL) _(ID) by 4 in the case of a DM-RS that linkswith a PSBCH.

This is an OCC configuration that maintains OCC mapping in two symbols(a first symbol and a third symbol out of four symbols) of which thelocations are the same as the existing D2D (ProSe). That is, in the caseof a DM-RS that links with a PSSCH, when remainders obtained by dividingn^(SA) _(ID) by 2 are 0 and 1, OCC values of a first symbol and a thirdsymbol are [+1 +1] and [+1, −1], respectively.

Further, in association with a cyclic shift, the configuration that isthe same as the configuration in D2D (ProSe) may be possible. However,different OCCs may be applied to two adjacent cyclic shift values, andthus, interference between neighbor UEs may be further reduced.

[Method 2-2 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, one of two symbolsthrough which a DM-RS is transmitted in each slot is a fourth symbol(symbol #3) of each slot in the same manner as a DM-RS that links withan existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe previous symbols (a first symbol (symbol #0), a second symbol(symbol #1), and a third symbol (symbol #2)) in the slot.

Also, this is the case in which an extended CP is used, one of twosymbols through which a DM-RS is transmitted in each slot is a thirdsymbol (symbol #2) of each slot, in the same manner as a DM-RS thatlinks with an existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe previous symbols (a first symbol (symbol #0) and a second symbol(symbol #1)) in the slot.

In this instance, this is the case in which the locations of two symbolsout of the four symbols in a single subframe are the same as thelocations of two symbols for D2D(ProSe) and the remaining two symbolsare added, and thus, V2X may always transmit a DM-RS through a total offour symbols by adding two symbols in addition to two existing symbolsin the single subframe. Alternatively, one out of two schemes may beselected and used, the schemes including a scheme (scheme #1) thattransmits a DM-RS through two existing symbols in a single subframe inthe same manner as D2D (ProSe), through a higher layer signaling such asRRC or the like, and a scheme (scheme #2) that transmits a DM-RS byadding two symbols in addition to the two existing symbols in the singlesubframe.

TABLE 11 Parameter PSSCH PSCCH Cyclic shift n_(cs,λ) └n_(ID)^(SA)/2┘mod8 0 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1+1 +1] if n_(ID) ^(SA) mod 4 = 0 [+1 +1 +1 +1] sequence [−1 +1 +1 −1] ifn_(ID) ^(SA) mod 4 = 1 [−1 +1 −1 +1] if n_(ID) ^(SA) mod 4 = 2 [+1 +1 −1−1] if n_(ID) ^(SA) mod 4 = 3 Parameter PSDCH PSBCH Cyclic shiftn_(cs,λ) 0 └N_(ID) ^(SL)/2┘mod8 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)w^(λ)(3)] [+1 +1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 4 = 0 sequence[−1 +1 +1 −1] if N_(ID) ^(SL) mod 4 = 1 [−1 +1 −1 +1] if N_(ID) ^(SL)mod 4 = 2 [+1 +1 −1 −1] if N_(ID) ^(SL) mod 4 = 3

As shown in Table 11, [+1 +1 +1 +1], [−1 +1 +1 −1], [−1 +1 −1 +1], and[+1 +1 −1 −1] may be used as four types of length 4 OCCs by taking intoconsideration the DM-RS transmission of a DM-RS that links with a PSSCHand a PSBCH through a total of 4 symbols in a single subframe.

The four length 4 OCCs, that is, [+1 +1 +1 +1], [−1 +1 +1 −1], [−1 +1 −1+1], and [+1 +1 −1 −1] may be used respectively for the cases havingremainders of 0, 1, 2, and 3 that are obtained by dividing n^(SA) _(ID)by 4 in the case of a DM-RS that links with a PSSCH, and may be usedrespectively for the cases having remainders of 0, 1, 2, and 3 that areobtained by dividing n^(SL) _(ID) by 4 in the case of a DM-RS that linkswith a PSBCH.

This is an OCC configuration that maintains OCC mapping in two symbols(a second symbol and a fourth symbol out of four symbols) of which thelocations are the same as the existing D2D (ProSe). That is, in the caseof a DM-RS that links with a PSSCH, when remainders obtained by dividingn^(SA) _(ID) by 2 are 0 and 1, OCC values of a second symbol and afourth symbol are [+1 +1] and [+1 −1], respectively. Also, in the caseof a DM-RS that links with a PSBCH, when remainders obtained by dividingn^(SL) _(ID) by 2 are 0 and 1, OCC values of a second symbol and afourth symbol are [+1 +1] and [+1 −1], respectively.

Further, in association with a cyclic shift, the configuration that isthe same as the configuration in D2D (ProSe) may be possible. However,different OCCs may be applied to two adjacent cyclic shift values, andthus, interference between neighbor UEs may be further reduced.

[Method 3-1 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, one of two symbolsthrough which a DM-RS is transmitted in each slot is a fourth symbol(symbol #3) of each slot, in the same manner as a DM-RS that links witha UL PUSCH or a DM-RS that links with a PSSCH/PSCCH/PDSCH/PSBCH inD2D(ProSe), and the other symbol is one of the subsequent symbols (afifth symbol (symbol #4), a sixth symbol (symbol #5), and a seventhsymbol (symbol #6)) in the slot.

Also, this is the case in which an extended CP is used, one of twosymbols through which a DM-RS is transmitted in each slot is a thirdsymbol (symbol #2) of each slot, in the same manner as a DM-RS thatlinks with an existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe subsequent symbols (a fourth symbol (symbol #3), a fifth symbol(symbol #4), and a sixth symbol (symbol #5)) in the slot.

In this instance, this is the case in which the locations of two symbolsout of the four symbols in a single subframe are the same as thelocations of two symbols for D2D(ProSe) and the remaining two symbolsare added, and thus, V2X may always transmit a DM-RS through a total offour symbols by adding two symbols in addition to two existing symbolsin the single subframe. Alternatively, one out of two schemes may beselected and used, the schemes including a scheme (scheme #1) thattransmits a DM-RS through two existing symbols in a single subframe inthe same manner as D2D (ProSe), through a higher layer signaling such asRRC or the like, and a scheme (scheme #2) that transmits a DM-RS byadding two symbols in addition to the two existing symbols in the singlesubframe.

TABLE 12 Parameter PSSCH PSCCH Cyclic shift n_(cs,λ) └n_(ID)^(SA)/4┘mod8 0 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1+1 +1] if n_(ID) ^(SA) mod 4 = 0 [+1 +1 +1 +1] sequence [+1 −1 −1 +1] ifn_(ID) ^(SA) mod 4 = 1 [+1 −1 +1 −1] if n_(ID) ^(SA) mod 4 = 2 [+1 +1 −1−1] if n_(ID) ^(SA) mod 4 = 3 Parameter PSDCH PSBCH Cyclic shiftn_(cs,λ) 0 └N_(ID) ^(SL)/4┘mod8 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)w^(λ)(3)] [+1 +1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 4 = 0 sequence[+1 −1 −1 +1] if N_(ID) ^(SL) mod 4 = 1 [+1 −1 +1 −1] if N_(ID) ^(SL)mod 4 = 2 [+1 +1 −1 −1] if N_(ID) ^(SL) mod 4 = 3

As shown in Table 12, [+1 +1 +1 +1], [+1 −1 −1 +1], [+1 −1 +1 −1], and[+1 +1 −1 −1] may be used as four types of length 4 OCCs by taking intoconsideration the DM-RS transmission of a DM-RS that links with a PSSCHand a PSBCH through a total of 4 symbols in a single subframe.

The four length 4 OCCs, that is, [+1 +1 +1 +1], [+1 −1 −1 +1], [+1 −1 +1−1], and [+1 +1 −1 −1] may be used respectively for the cases havingremainders of 0, 1, 2, and 3 that are obtained by dividing n^(SA) _(ID)by 4 in the case of a DM-RS that links with a PSSCH, and may be usedrespectively for the cases having remainders of 0, 1, 2, and 3 that areobtained by dividing n^(SL) _(ID) by 4 in the case of a DM-RS that linkswith a PSBCH.

This is an OCC configuration that maintains OCC mapping in two symbols(a first symbol and a third symbol out of four symbols) of which thelocations are the same as the existing D2D (ProSe). That is, in the caseof a DM-RS that links with a PSSCH, when remainders obtained by dividingn^(SA) _(ID) by 2, OCC values of a first symbol and a third symbol are[+1 +1] and [+1 −1], respectively.

Further, in association with a cyclic shift, in the case of a DM-RS thatlinks with a PSSCH in D2D (ProSe), one out of 8 cyclic shift values isdetermined by executing modulo8 (mod 8) on a value obtained by dividingn^(SA) _(ID) by 2, whereas, in the case of a DM-RS that links with aPSSCH in V2X, one out of 8 cyclic shift values is determined byexecuting modulo8 (mod 8) on a value obtained by dividing n^(SA) _(ID)by 4. In the same manner, in the case of a DM-RS that links with a PSBCHin D2D (ProSe), one out of 8 cyclic shift values is determined byexecuting modulo8 (mod 8) on a value obtained by dividing n^(SL) _(ID)by 2, whereas, in the case of a DM-RS that links with a PSBCH in V2X,one out of 8 cyclic shift values is determined by executing modulo 8(mod 8) on a value obtained by dividing n^(SL) _(ID) by 4. Further, inthe case of a DM-RS that links with a PSBCH in D2D (ProSe), one out of30 sequence shift patterns f_(ss) in group hopping is determined byexecuting modulo30 (mod 30) on a value obtained by dividing n^(SL) _(ID)by 16, whereas, in the case of a DM-RS that links with a PSBCH in V2X,one out of 30 sequence shift patterns f_(ss) in group hopping isdetermined by executing modulo 30 (mod 30) on a value obtained bydividing n^(SL) _(ID) by 32.

[Method 3-2 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, one of two symbolsthrough which a DM-RS is transmitted in each slot is a fourth symbol(symbol #3) of each slot in the same manner as a DM-RS that links withan existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe previous symbols (a first symbol (symbol #0), a second symbol(symbol #1), and a third symbol (symbol #2)).

Also, this is the case in which an extended CP is used, one of twosymbols through which a DM-RS is transmitted in each slot is a thirdsymbol (symbol #2) of each slot, in the same manner as a DM-RS thatlinks with an existing UL PUSCH or a DM-RS that links with aPSSCH/PSCCH/PDSCH/PSBCH in D2D(ProSe), and the other symbol is one ofthe previous symbols (a first symbol (symbol #0) and a second symbol(symbol #1)).

In this instance, this is the case in which the locations of two symbolsout of the four symbols in a single subframe are the same as thelocations of two symbols for D2D(ProSe) and the remaining two symbolsare added, and thus, V2X may always transmit a DM-RS through a total offour symbols by adding two symbols in addition to two existing symbolsin the single subframe. Alternatively, one out of two schemes may beselected and used, the schemes including a scheme (scheme #1) thattransmits a DM-RS through two existing symbols in a single subframe inthe same manner as D2D (ProSe), through a higher layer signaling such asRRC or the like, and a scheme (scheme #2) that transmits a DM-RS byadding two symbols in addition to the two existing symbols in the singlesubframe.

TABLE 13 Parameter PSSCH PSCCH Cyclic shift n_(cs,λ) └n_(ID)^(SA)/4┘mod8 0 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1+1 +1] if n_(ID) ^(SA) mod 4 = 0 [+1 +1 +1 +1] sequence [−1 +1 +1 −1] ifn_(ID) ^(SA) mod 4 = 1 [−1 +1 −1 +1] if n_(ID) ^(SA) mod 4 = 2 [+1 +1 −1−1] if n_(ID) ^(SA) mod 4 = 3 Parameter PSDCH PSBCH Cyclic shiftn_(cs,λ) 0 └N_(ID) ^(SL)/4┘mod8 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)w^(λ)(3)] [+1 +1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 4 = 0 sequence[−1 +1 +1 −1] if N_(ID) ^(SL) mod 4 = 1 [−1 +1 −1 +1] if N_(ID) ^(SL)mod 4 = 2 [+1 +1 −1 −1] if N_(ID) ^(SL) mod 4 = 3

As shown in Table 13, [+1 +1 +1 +1], [−1 +1 +1 −1], [−1 +1 −1 +1], and[+1 +1 −1 −1] may be used as four types of length 4 OCCs by taking intoconsideration the DM-RS transmission of a DM-RS that links with a PSSCHand a PSBCH through a total of 4 symbols in a single subframe.

The four length 4 OCCs, that is, [+1 +1 +1 +1], [−1 +1 +1 −1], [−1 +1 −1+1], and [+1 +1 −1 −1] may be used respectively for the cases havingremainders of 0, 1, 2, and 3 that are obtained by dividing n^(SA) _(ID)by 4 in the case of a DM-RS that links with a PSSCH, and may be usedrespectively for the cases having remainders of 0, 1, 2, and 3 that areobtained by dividing n^(SL) _(ID) by 4 in the case of a DM-RS that linkswith a PSBCH.

This is an OCC configuration that maintains OCC mapping in two symbols(a second symbol and a fourth symbol out of four symbols) of which thelocations are the same as the existing D2D (ProSe). That is, in the caseof a DM-RS that links with a PSSCH, when remainders obtained by dividingn^(SA) _(ID) by 2 are 0 and 1, OCC values of a second symbol and afourth symbol are [+1 +1] and [+1 −1], respectively.

Further, in association with a cyclic shift, in the case of a DM-RS thatlinks with a PSSCH in D2D (ProSe), one out of 8 cyclic shift values isdetermined by executing modulo8 (mod 8) on a value obtained by dividingn^(SA) _(ID) by 2, whereas, in the case of a DM-RS that links with aPSSCH in V2X, one out of 8 cyclic shift values may be determined byexecuting modulo 8 (mod 8) on a value obtained by dividing n^(SA) _(ID)by 4. In the same manner, in the case of a DM-RS that links with a PSBCHin D2D (ProSe), one out of 8 cyclic shift values is determined byexecuting modulo 8 (mod 8) on a value obtained by dividing n^(SL) _(ID)by 2, whereas, in the case of a DM-RS that links with a PSBCH in V2X,one out of 8 cyclic shift values may be determined by executing modulo 8(mod 8) on a value obtained by dividing n^(SL) _(ID) by 4. Further, inthe case of a DM-RS that links with a PSBCH in D2D (ProSe), one out of30 sequence shift patterns f_(ss) in group hopping is determined byexecuting modulo30 (mod 30) on a value obtained by dividing n^(SL) _(ID)by 16, whereas, in the case of a DM-RS that links with a PSBCH in V2X,one out of 30 sequence shift patterns f_(ss) in group hopping may bedetermined by executing modulo30 (mod 30) on a value obtained bydividing n^(SL) _(ID) by 32.

Subsequently, the case in which two types of OCCs are used like the D2D(ProSe) and the length of an OCC is 4 (method 4 for an orthogonalsequence (OCC) and a cyclic shift) may be considered for V2X, whereastwo length 2 OCCs are used in the case of D2D (ProSe). Although this maybe applied to the example illustrated in the part (b) of FIG. 5, thepresent disclosure may not be limited thereto.

[Method 4 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used and, two symbols out ofseven symbols in each of a first slot and a second slot are determinedas symbols through which a DM-RS is transmitted.

Also, this is the case in which an extended CP is used and, two symbolsout of six symbols in each of a first slot and a second slot aredetermined as symbols through which a DM-RS is transmitted.

To this end, one out of two schemes may be selected and used, theschemes including a scheme (scheme #1) that transmits a DM-RS throughtwo existing symbols in a single subframe in the same manner as D2D(ProSe), through a higher layer signaling such as RRC or the like, and ascheme (scheme #2) that transmits a DM-RS through a total of foursymbols in the single subframe.

TABLE 14 Parameter PSSCH PSCCH Cyclic n_(cs,λ) └n_(ID) ^(SA)/2┘mod8 0shift Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1 +1 +1] ifn_(ID) ^(SA) mod 2 = 0 [+1 +1 +1 +1] sequence [+1 −1 +1 −1] if n_(ID)^(SA) mod 2 = 1 Parameter PSDCH PSBCH Cyclic n_(cs,λ) 0 └N_(ID)^(SL)/2┘mod8 shift Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1+1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 2 = 0 sequence [+1 −1 +1 −1]if N_(ID) ^(SL) mod 2 = 1

As shown in Table 14, [+1 +1 +1 +1] and [+1 −1 +1 −1] may be used as twotypes of length 4 OCCs by taking into consideration the DM-RStransmission of a DM-RS that links with a PSSCH and a PSBCH through atotal of 4 symbols in a single subframe.

The two length 4 OCCs, that is, [+1 +1 +1 +1] and [+1 −1 +1 −1] may beused respectively for the cases having remainders of 0 and 1 that areobtained by dividing n^(SA) _(ID) by 2 in the case of a DM-RS that linkswith a PSSCH, and may be used respectively for the cases havingremainders of 0 and 1 that are obtained by dividing n^(SL) _(ID) by 2 inthe case of a DM-RS that links with a PSBCH.

Further, in association with a cyclic shift, the configuration that isthe same as the configuration in D2D (ProSe) may be possible.

Subsequently, the case in which the number of types of OCCs is extendedto 4 and the length of an OCC is 4 (method 5 and method 6 for anorthogonal sequence (OCC) and a cyclic shift) may be considered for V2X,whereas two length 2 OCCs are used in the case of D2D (ProSe). Althoughthis may be applied to the example illustrated in the part (b) of FIG.5, the present disclosure may not be limited thereto.

[Method 5 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used and two symbols out ofseven symbols in each of a first slot and a second slot are determinedas symbols through which a DM-RS is transmitted.

Also, this is the case in which an extended CP is used and two symbolsout of six symbols in each of a first slot and a second slot aredetermined as symbols through which a DM-RS is transmitted.

To this end, one out of two schemes may be selected and used, theschemes including a scheme (scheme #1) that transmits a DM-RS throughtwo existing symbols in a single subframe in the same manner as D2D(ProSe), through a higher layer signaling such as RRC or the like, and ascheme (scheme #2) that transmits a DM-RS through a total of foursymbols in the single subframe.

TABLE 15 Parameter PSSCH PSCCH Cyclic shift n_(cs,λ) └n_(ID)^(SA)/2┘mod8 0 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1+1 +1] if n_(ID) ^(SA) mod 4 = 0 [+1 +1 +1 +1] sequence [+1 −1 +1 −1] ifn_(ID) ^(SA) mod 4 = 1 [+1 +1 −1 −1] if n_(ID) ^(SA) mod 4 = 2 [+1 −1 −1+1] if n_(ID) ^(SA) mod 4 = 3 Parameter PSDCH PSBCH Cyclic shiftn_(cs,λ) 0 └N_(ID) ^(SL)/2┘mod8 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)w^(λ)(3)] [+1 +1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 4 = 0 sequence[+1 −1 +1 −1] if N_(ID) ^(SL) mod 4 = 1 [+1 +1 −1 −1] if N_(ID) ^(SL)mod 4 = 2 [+1 −1 −1 +1] if N_(ID) ^(SL) mod 4 = 3

As shown in Table 15, [+1 +1 +1 +1], [+1 −1 +1 −1], [+1 +1 −1 −1], and[+1 −1 −1 +1] may be used as four types of length 4 OCCs by taking intoconsideration the DM-RS transmission of a DM-RS that links with a PSSCHand a PSBCH through a total of 4 symbols in a single subframe.

The four length 4 OCCs, that is, [+1 +1 +1 +1], [+1 −1 +1 −1], [+1 +1 −1−1], and [+1 −1 −1 +1] may be used respectively for the cases havingremainders of 0, 1, 2, and 3 that are obtained by dividing n^(SA) _(ID)by 4 in the case of a DM-RS that links with a PSSCH, and may be usedrespectively for the cases having remainders of 0, 1, 2, and 3 that areobtained by dividing n^(SL) _(ID) by 4 in the case of a DM-RS that linkswith a PSBCH.

Further, in association with a cyclic shift, the configuration that isthe same as the configuration in D2D (ProSe) may be possible. However,different OCCs may be applied to two adjacent cyclic shift values andthus, interference between neighbor UEs may be further reduced.

[Method 6 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used and two symbols out ofseven symbols in each of a first slot and a second slot are determinedas symbols through which a DM-RS is transmitted.

Also, this is the case in which an extended CP is used and two symbolsout of six symbols in each of a first slot and a second slot aredetermined as symbols through which a DM-RS is transmitted.

To this end, one out of two schemes may be selected and used, theschemes including a scheme (scheme #1) that transmits a DM-RS throughtwo existing symbols in a single subframe in the same manner as D2D(ProSe), through a higher layer signaling such as RRC or the like, and ascheme (scheme #2) that transmits a DM-RS through a total of foursymbols in the single subframe.

TABLE 16 Parameter PSSCH PSCCH Cyclic shift n_(cs,λ) └n_(ID)^(SA)/4┘mod8 0 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2) w^(λ)(3)] [+1 +1+1 +1] if n_(ID) ^(SA) mod 4 = 0 [+1 +1 +1 +1] sequence [+1 −1 +1 −1] ifn_(ID) ^(SA) mod 4 = 1 [+1 +1 −1 −1] if n_(ID) ^(SA) mod 4 = 2 [+1 −1 −1+1] if n_(ID) ^(SA) mod 4 = 3 Parameter PSDCH PSBCH Cyclic shiftn_(cs,λ) 0 └N_(ID) ^(SL)/4┘mod8 Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)w^(λ)(3)] [+1 +1 +1 +1] [+1 +1 +1 +1] if N_(ID) ^(SL) mod 4 = 0 sequence[+1 −1 +1 −1] if N_(ID) ^(SL) mod 4 = 1 [+1 +1 −1 −1] if N_(ID) ^(SL)mod 4 = 2 [+1 −1 −1 +1] if N_(ID) ^(SL) mod 4 = 3

As shown in Table 16, [+1 +1 +1 +1], [+1 −1 +1 −1], [+1 +1 −1 −1], and[+1 −1 −1 +1] may be used as four types of length 4 OCCs by taking intoconsideration the DM-RS transmission of a DM-RS that links with a PSSCHand a PSBCH through a total of 4 symbols in a single subframe.

The four length 4 OCCs, that is, [+1 +1 +1 +1], [+1 −1 +1 −1], [+1 +1 −1−1], and [+1 −1 −1 +1] may be used respectively for the cases havingremainders of 0, 1, 2, and 3 that are obtained by dividing n^(SA) _(ID)by 4 in the case of a DM-RS that links with a PSSCH, and may be usedrespectively for the cases having remainders of 0, 1, 2, and 3 that areobtained by dividing n^(SL) _(ID) by 4 in the case of a DM-RS that linkswith a PSBCH.

Further, in association with a cyclic shift, in the case of a DM-RS thatlinks with a PSSCH in D2D (ProSe), one out of 8 cyclic shift values isdetermined by executing modulo8 (mod 8) on a value obtained by dividingn^(SA) _(ID) by 2, whereas, in the case of a DM-RS that links with aPSSCH in V2X, one out of 8 cyclic shift values may be determined byexecuting modulo8 (mod 8) on a value obtained by dividing n^(SA) _(ID)by 4. In the same manner, in the case of a DM-RS that links with a PSBCHin D2D (ProSe), one out of 8 cyclic shift values is determined byexecuting modulo8 (mod 8) on a value obtained by dividing n^(SL) _(ID)by 2, whereas, in the case of a DM-RS that links with a PSBCH in V2X,one out of 8 cyclic shift values is determined by executing modulo 8(mod 8) on a value obtained by dividing n^(SL) _(ID) by 4. Further, inthe case of a DM-RS that links with a PSBCH in D2D (ProSe), one out of30 sequence shift patterns f_(ss) in group hopping is determined byexecuting modulo 30 (mod 30) on a value obtained by dividing n^(SL)_(ID) by 16, whereas, in the case of a DM-RS that links with a PSBCH inV2X, one out of 30 sequence shift patterns f_(ss) in group hopping maybe determined by executing modulo30 (mod 30) on a value obtained bydividing n^(SL) _(ID) by 32.

Subsequently, the case in which two types of OCCs are used like the D2D(ProSe) and the length of an OCC is 3 (method 7 for an orthogonalsequence (OCC) and cyclic shift) may be considered for V2X, whereas twolength 2 OCCs are used in the case of D2D (ProSe). Although this may beapplied to the example illustrated in the part (c) of FIG. 5, thepresent disclosure may not be limited thereto.

[Method 7 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, and three symbols out of14 symbols in a single subframe are determined as symbols through whicha DM-RS is transmitted.

Also, this is the case in which an extended CP is used, and threesymbols out of 12 symbols in a single subframe are determined as symbolsthrough which a DM-RS is transmitted.

To this end, one out of two schemes may be selected and used, theschemes including a scheme (scheme #1) that transmits a DM-RS throughtwo existing symbols in a single subframe in the same manner as D2D(ProSe), through a higher layer signaling such as RRC or the like, and ascheme (scheme #2) that transmits a DM-RS through a total of threesymbols in the single subframe.

TABLE 17 Parameter PSBCH Cyclic shift n_(cs,λ) └N_(ID) ^(SL)/2┘mod8Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)] [+1 +1 +1] if N_(ID) ^(SL) mod 2= 0 sequence [+1 e^(j2π/3) e^(j4π/3)] if N_(ID) ^(SL) mod 2 = 1

As shown in Table 17, [+1 +1 +1] and [+1 e^(j2π/3) e^(j4π/3)] may beused as two types of length 3 OCCs by taking into consideration theDM-RS transmission of a DM-RS that links with a PSBCH through a total of3 symbols in a single subframe. Alternatively, [+1 +1 +1] and [+1e^(j4π/3) e^(j2π/3)] may be used as the two types of length 3 OCCs.

Each of the two length 3 OCCs, that is, [+1 +1 +1] and [+1 e^(j2π/3)e^(j4π/3)] (or [+1 +1 +1] and [+1 e^(j4π/3) e^(j2π/3)]) may be usedrespectively for the cases having remainders of 0 and 1 that areobtained by dividing n^(SL) _(ID) by 2 in the case of a DM-RS that linkswith a PSBCH.

Further, in association with a cyclic shift, the configuration that isthe same as the configuration in D2D (ProSe) may be possible.

Subsequently, the case in which the number of types of OCCs is extendedto 3 and the length of an OCC is 3 (method 8 and method 9 for anorthogonal sequence (OCC) and a cyclic shift) may be considered for V2X,whereas two length 2 OCCs are used in the case of D2D (ProSe). Althoughthis may be applied to the example illustrated in the part (c) of FIG.5, the present disclosure may not be limited thereto.

[Method 8 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, and three symbols out of14 symbols in a single subframe are determined as symbols through whicha DM-RS is transmitted.

Also, this is the case in which an extended CP is used, and threesymbols out of 12 symbols in a single subframe are determined as symbolsthrough which a DM-RS is transmitted.

To this end, one out of two schemes may be selected and used, theschemes including a scheme (scheme #1) that transmits a DM-RS throughtwo existing symbols in a single subframe in the same manner as D2D(ProSe), through a higher layer signaling such as RRC or the like, and ascheme (scheme #2) that transmits a DM-RS through a total of threesymbols in the single subframe.

TABLE 18 Parameter PSBCH Cyclic shift n_(cs,λ) └N_(ID) ^(SL)/2┘mod8Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)] [+1 +1 +1] if N_(ID) ^(SL) mod 3= 0 sequence [+1 e^(j2π/3) e^(j4π/3)] if N_(ID) ^(SL) mod 3 = 1 [+1e^(j4π/3) e^(j2π/3)] if N_(ID) ^(SL) mod 3 = 2

As shown in Table 18, [+1 +1 +1], [+1 e^(j2π/3) e^(j4π/3)], and [+1e^(j4π/3) e^(j2π/3)] may be used as three types of length 3 OCCs bytaking into consideration the DM-RS transmission of a DM-RS that linkswith a PSBCH through a total of 3 symbols in a single subframe.

Each of the three length 3 OCCs, that is, [+1 +1 +1], [+1 e^(j2π/3)e^(j4π/3)], and [+1 e^(j4π/3) e^(j2π/3)] may be used respectively forthe cases having remainders of 0, 1, and 2 that are obtained by dividingn^(SL) _(ID) by 3 in the case of a DM-RS that links with a PSBCH.

Further, in association with a cyclic shift, the configuration that isthe same as the configuration in D2D (ProSe) may be possible.

[Method 9 for Orthogonal Sequence (OCC) and Cyclic Shift]

This is the case in which a normal CP is used, and three symbols out of14 symbols in a single subframe are determined as symbols through whicha DM-RS is transmitted.

Also, this is the case in which an extended CP is used, and threesymbols out of 12 symbols in a single subframe are determined as symbolsthrough which a DM-RS is transmitted.

To this end, one out of two schemes may be selected and used, theschemes including a scheme (scheme #1) that transmits a DM-RS throughtwo existing symbols in a single subframe in the same manner as D2D(ProSe), through a higher layer signaling such as RRC or the like, and ascheme (scheme #2) that transmits a DM-RS through a total of threesymbols in the single subframe.

TABLE 19 Parameter PSBCH Cyclic shift n_(cs,λ) └N_(ID) ^(SL)/3┘mod8Orthogonal [w^(λ)(0) w^(λ)(1) w^(λ)(2)] [+1 +1 +1] if N_(ID) ^(SL) mod 3= 0 sequence [+1 e^(j2π/3) e^(j4π/3)] if N_(ID) ^(SL) mod 3 = 1 [+1e^(j4π/3) e^(j2π/3)] if N_(ID) ^(SL) mod 3 = 2

As shown in Table 19, [+1 +1 +1], [+1 e^(j2π/3) e^(j4π/3)], and [+1e^(j4π/3) e^(j2π/3)] may be used as three types of length 3 OCCs bytaking into consideration the DM-RS transmission of a DM-RS that linkswith a PSBCH through a total of 3 symbols in a single subframe.

Each of the three length 3 OCCs, that is, [+1 +1 +1], [+1 e^(j2π/3)e^(j4π/3)], and [+1 e^(j4π/3) e^(j2π/3)] may be used respectively forthe cases having remainders of 0, 1, and 2 that are obtained by dividingn^(SL) _(ID) by 3 in the case of a DM-RS that links with a PSBCH.

Further, in association with a cyclic shift, in the case of a DM-RS thatlinks with a PSBCH in D2D (ProSe), one out of 8 cyclic shift values isdetermined by executing modulo8 (mod 8) on a value obtained by dividingn^(SL) _(ID) by 2, whereas, in the case of a DM-RS that links with aPSBCH in V2X, one out of 8 cyclic shift values is determined byexecuting modulo8 (mod 8) on a value obtained by dividing n^(SL) _(ID)by 3. Further, in the case of a DM-RS that links with a PSBCH in D2D(ProSe), one out of 30 sequence shift patterns f_(ss) in group hoppingis determined by executing modulo30 (mod 30) on a value obtained bydividing n^(SL) _(ID) by 16, whereas, in the case of a DM-RS that linkswith a PSBCH in V2X, one out of 30 sequence shift patterns f_(ss) ingroup hopping is determined by executing modulo 30 (mod 30) on a valueobtained by dividing n^(SL) _(ID) by 24.

Here, each embodiment may be applied differently to each channel (PSCCH,PSSCH, PSDCH, and PSBCH) that links with a DM-RS. For example, in thecase of a DM-RS that links with a PSCCH and a PSSCH, one of Method 4 foran orthogonal sequence (OCC) and a cyclic shift, Method 5 for anorthogonal sequence (OCC) and a cyclic shift, and Method 6 for anorthogonal sequence (OCC) and a cyclic shift may be used. However, inthe case of a DM-RS that links with a PSBCH, one of Method 7 for anorthogonal sequence (OCC) and a cyclic shift, Method 8 for an orthogonalsequence (OCC) and a cyclic shift, and Method 9 for an orthogonalsequence (OCC) and a cyclic shift may be used.

In addition, n_(CS,λ) is determined to be one out of a total of eightvalues which are determined through Table 6 to Table 19. In thisinstance, only 0, π/6, π/3, π/2, 4π/6, 5π/6, π, and 7π/6 are used basedon α_(λ)=2πn_(cs,λ)/12 and thus, the value is not equally allocated withrespect to 360 degrees, which is a drawback. Therefore, through Table 20or 21, one out of a total of 8 cyclic shift values which are determinedthrough Table 6 to Table 19 may indicate n⁽¹⁾ _(DMRS) or n⁽²⁾ _(DMRS,λ)in Equation 5 below, as opposed to indicating n_(CS,λ). That is, when atotal of 8 cyclic shifts determined through Table 6 to Table 19 are 0,1, 2, 3, 4, 5, 6, and 7, respectively, this indicates that n_(CS,λ)value is 0, 1, 2, 3, 4, 5, 6, and 7, respectively. According to Table 20in the present disclosure, when a total of 8 cyclic shifts determinedthrough Table 6 to Table 19 are 0, 1, 2, 3, 4, 5, 6, and 7,respectively, this indicates that n⁽¹⁾ _(DMRS) value is 0, 2, 3, 4, 6,8, 9, and 10, respectively. According to Table 21 in the presentdisclosure, when a total of 8 cyclic shifts determined through Table 6to Table 19 are 0, 1, 2, 3, 4, 5, 6, and 7, respectively, this indicatesthat n⁽²⁾ _(DMRS,λ) value is 0, 6, 3, 4, 2, 8, 10, and 9, respectively.

n _(cs,λ)=(n _(DMRS) ⁽¹⁾ +n _(DMRS,λ) ⁽²⁾ +n _(PN)(n_(s)))mod12  [Equation 5]

TABLE 20 cyclicShift n_(DMRS) ⁽¹⁾ 0 0 1 2 2 3 3 4 4 6 5 8 6 9 7 10 

TABLE 21 cyclicShift n_(DMRS,A) ⁽²⁾ 0 (000) 0 1 (001) 6 2 (010) 3 3(011) 4 4 (100) 2 5 (101) 8 6 (110) 10  7 (111) 9

Here, the following cases are possible with respect to n_(CS,λ) that isdetermined by adding three values, that is, n⁽¹⁾ _(DMRS), n⁽²⁾_(DMRS,λ), and n_(PN), as shown in Equation 5, and executing modulo12(mod 12) on the sum.

1) the case #1 in which a total of 8 cyclic shifts determined throughTable 6 to Table 19 indicate n⁽¹⁾ _(DMRS)

-   -   determine n⁽¹⁾ _(DMRS) based on Table 20    -   n⁽²⁾ _(DMRS,λ)=0    -   n_(PN)=0

2) the case #1 in which a total of 8 cyclic shifts determined throughTable 6 to Table 19 indicate n⁽²⁾ _(DMRS,λ)

-   -   n⁽¹⁾ _(DMRS)=0    -   determine n⁽²⁾ _(DMRS,λ) based on Table 21    -   n_(PN)=0

3) the case #1 in which a total of 8 cyclic shifts determined throughTable 6 to Table 19 indicate n⁽¹⁾ _(DMRS) and n⁽²⁾ _(DMRS,λ)

-   -   determine n⁽¹⁾ _(DMRS) based on Table 20    -   determine n⁽²⁾ _(DMRS,λ) based on Table 21    -   n_(PN)=0

4) the case #2 in which a total of 8 cyclic shifts determined throughTable 6 to Table 19 indicate n⁽¹⁾ _(DMRS)

-   -   determine n⁽¹⁾ _(DMRS) based on Table 20    -   n⁽²⁾ _(DMRS,λ)=0    -   n_(PN) is generated to be different for each DM-RS transmission        symbol

5) the case #2 in which a total of 8 cyclic shifts determined throughTable 6 to Table 19 indicate n⁽²⁾ _(DMRS,λ)

-   -   n⁽¹⁾ _(DMRS)=0    -   determine n⁽²⁾ _(DMRS,λ) based on Table 21    -   n_(PN) is generated to be different for each DM-RS transmission        symbol

6) the case #2 in which a total of 8 cyclic shifts determined throughTable 6 to Table 19 indicate n⁽¹⁾ _(DMRS) and n⁽²⁾ _(DMRS,λ)

-   -   determine n⁽¹⁾ _(DMRS) based on Table 20    -   determine n⁽²⁾ _(DMRS,λ) based on Table 21    -   n_(PN) is generated to be different for each DM-RS transmission        symbol

Among the above described cases, the case that generates n_(PN) to bedifferent for each DM-RS transmission symbol is to avoid an identicalDM-RS that is transmitted by a terminal in a single subframe (ortransmission time interval (TTI)) by taking into consideration theenvironment where a terminal has a very quick movement speed. Methods toachieve the above will be described as follows.

Hereinafter, method 1 for generating n_(PN) to be different for eachDM-RS transmission symbol is defined.

According to method 1, as shown in Equation 6 below, by taking intoconsideration the case in which a DM-RS is generated in two symbols in asingle slot which corresponds to the part (a) of FIG. 5 or the part (b)of FIG. 5, two different n_(PN) values are defined in each slot,irrespective of the locations of the two symbols. One n_(PN) value isapplied to a first symbol through which a DM-RS is transmitted in theslot, and the other n_(PN) value is applied to a second symbol throughwhich the DM-RS is transmitted in the slot. In this instance, l′=0 or 1.

n _(PN)(n _(s))=Σ_(i=0) ⁷ c(16n _(ss) ^(PSSCH)+8l′+i)·2^(i)  [Equation6]

Here, c(i) denotes a pseudo-random sequence defined as Gold sequencehaving a degree of 31.

A pseudo-random sequence generator for the pseudo-random sequence isinitialized to

$c_{init} = {{\left\lfloor \frac{n_{ID}^{SA}}{30} \right\rfloor \cdot 2^{5}} + \left( {n_{ID}^{SA}{mod}\; 30} \right)}$

at the beginning of each slot that satisfies n^(PSSCH) _(ss)=0.

In this instance, n^(PSSCH) _(ss) denotes a current slot number in thesubframe pool for a sidelink. Here, n^(SA) _(ID) may be a sidelink groupdestination identity.

Hereinafter, method 2 for generating n_(PN) to be different for eachDM-RS transmission symbol is defined.

According to method 2, as shown in Equation 7 below, by taking intoconsideration the case in which a DM-RS is generated in three symbols ina single subframe which corresponds to the part (c) of FIG. 5, threedifferent n_(PN) values are defined in each subframe, irrespective ofthe locations of the three symbols. A first n_(PN) value is applied to afirst symbol through which a DM-RS is transmitted in the subframe, asecond n_(PN) value is applied to a second symbol through which theDM-RS is transmitted in the subframe, and a third n_(PN) value isapplied to a third symbol through which the DM-RS is transmitted in thesubframe. In this instance, l′=0, 1, or 2.

n _(PN)(n _(s))=Σ_(i=0) ⁷ c(8l′+i)·2^(i)  [Equation 7]

Also, c(i) denotes a pseudo-random sequence defined as Gold sequencehaving a degree of 31.

The pseudo-random sequence generator for the pseudo-random sequence isinitialized to

${c_{init} = {{\left\lfloor \frac{N_{ID}^{SL}}{30} \right\rfloor \cdot 2^{5}} + {\left( {N_{ID}^{SL}{mod}\; 30} \right)\mspace{14mu} {or}}}}\mspace{14mu}$${c_{init} = {{\left\lfloor \frac{\left\lfloor {N_{ID}^{SL}\text{/}24} \right\rfloor}{30} \right\rfloor \cdot 2^{5}} + \left( {\left\lfloor {N_{ID}^{SL}\text{/}24} \right\rfloor {mod}\; 30} \right)}},$

at the beginning of each PSBCH subframe (a subframe that transmits aPSBCH).

Here, N^(SL) _(ID) may be a physical layer sidelink synchronizationidentity.

Hereinafter, method 3 for generating n_(PN) to be different for eachDM-RS transmission symbol is defined.

Method 3 defines a different n_(PN) value for each of the symbols in asingle slot, and a corresponding symbol through which a DM-RS istransmitted applies a corresponding n_(PN) value of the symbol, as shownin Equation 8 below. This may be applied to all of the cases illustratedthrough FIGS. 5A, 5B, and 5C. In this instance, N^(SL) _(symb) denotesthe number of symbols in a single slot in a sidelink (SL) (7 in the caseof a normal CP, and 6 in the case of an extended CP), and l=0, 1, . . ., N^(SL) _(symb) denotes a symbol index in a single slot.

n _(PN)(n _(s))=Σ_(i=0) ⁷ c(8·N _(symb) ^(SL) ·n_(s)+8l+i)·2^(i)  [Equation 8]

In Equation 8, n_(s) is n^(PSSCH) _(ss) when the equation is applied toa DM-RS for a PSSCH.

However, in Equation 8, n_(s) may have two values, that is, 0 or 1, whenthe equation is applied to a DM-RS for a PSBCH.

Also, c(i) denotes a pseudo-random sequence defined as Gold sequencehaving a degree of 31.

When Equation 8 is applied to the DM-RS for the PSSCH, the pseudo-randomsequence generator for the pseudo-random sequence may be initialized to

$c_{init} = {{\left\lfloor \frac{n_{ID}^{SA}}{30} \right\rfloor \cdot 2^{5}} + \left( {n_{ID}^{SA}{mod}\; 30} \right)}$

at the beginning of each slot that satisfies n^(PSSCH) _(ss)=0.

When Equation 8 is applied to the DM-RS for the PSCBCH, thepseudo-random sequence generator for the pseudo-random sequence may beinitialized to

${c_{init} = {{\left\lfloor \frac{N_{ID}^{SL}}{30} \right\rfloor \cdot 2^{5}} + {\left( {N_{ID}^{SL}{mod}\; 30} \right)\mspace{14mu} {or}}}}\mspace{14mu}$${c_{init} = {{\left\lfloor \frac{\left\lfloor {N_{ID}^{SL}\text{/}24} \right\rfloor}{30} \right\rfloor \cdot 2^{5}} + \left( {\left\lfloor {N_{ID}^{SL}\text{/}24} \right\rfloor {mod}\; 30} \right)}},$

at the beginning of every PSBCH subframe (a subframe that transmits aPSBCH).

In this instance, n^(PSSCH) _(ss) denotes a current slot number in thesubframe pool for a sidelink. Here, n^(SA) _(ID) is a sidelink groupdestination identity, and N^(SL) _(ID) is a physical layer sidelinksynchronization identity.

FIG. 6 is a block diagram illustrating a wireless communication systemaccording to an embodiment of the present invention.

Referring to FIG. 6, the UE 300 includes a processor 310, a radiofrequency (RF) module 305 and a memory 315. The memory 315 is connectedto the processor 310 and stores various pieces of information to drivethe processor 310. The RF module 305 is connected to the processor 310and transmits and/or receives a radio signal. For example, the RF module305 receives an upper-layer message, such as a RRC (connectionreconfiguration) message, and a SIB message from the BS 350. Also the RFmodule 305 transmits an uplink signal according to an embodiment of thepresent invention. The processor 310 implements functions, processesand/or methods of the UE suggested in FIGS. 2 to 5 in the presentspecification. The memory 315 may store with various values calculatedby using equations and tables, and provide inputs to the processor 310based on request of order from the processor 310.

The BS 350 includes a processor 355, a Radio Frequency (RF) module 365,and a memory 360. The memory 360 is connected to the processor 355, andstores various pieces of information for driving the processor 355. TheRF module 365 is connected with the processor 355, and transmits and/orreceives a wireless signal. The processor 355 implements functions,processes and/or methods of the BS suggested in FIGS. 2 to 5 in thepresent specification.

Exemplary embodiments of the present invention may be implemented byhardware, software or a combination thereof. In a hardwareconfiguration, the above-described functions and operations may beperformed by one or more processors, such as a microprocessor, acontroller, a microcontroller, or an ASIC (Application SpecificIntegrated Circuit), a DSP (Digital Signal Processor), a PLD(Programmable logic device), a FPGA (Field Programmable Gate Array),and/or combinations thereof configured to perform the functions andoperations. In a software configuration, software or program codes toperform the functions and operations may be implemented as modules.Software may be stored in one or more memory units and may be executedby the one or more processors. It will be apparent to those of ordinaryskill in the art from the description of the present invention todesign, develop and implement the memory units or the processors.

A processor according to an embodiment of the present disclosure maydetermine group hopping, an orthogonal sequence (OCC), and a cyclicshift value based on the methods described through Table 6 to Table 19.

Also, in the case of a cyclic shift n_(CS,λ) value in Table 6 to Table19, the processor may execute a control so that at least one out of n⁽¹⁾_(DMRS) or n⁽²⁾ _(DMRS,λ) in Equation 5 is indicated through Table 20 orTable 21 as opposed to applying the methods described through Table 6 toTable 19 as they are, by taking into consideration a drawback in thatonly 0, π/6, π/3, π/2, 4π/6, 5π/6, π, and 7π/6 are used based onα_(λ)=2πn_(cs,λ)/12 and the value is not equally allocated with respectto 360 degrees.

According to one or more exemplary embodiments, an apparatus and methodfor transmitting Demodulation-Reference Signal (DM-RS) configured forVehicle-to-everything (V2X) communication are provided. An apparatus maybe equipped in a vehicle, such as a car, motorcycle, and the like.However, the apparatus may be equipped in other devices configured for aV2X communication.

The apparatus may include a processor, a memory, and a wirelesstransceiver including an RF module and an antenna. The processor maygenerate a first DM-RS for V2X communication and a second DM-RS for V2Xcommunication, the first DM-RS for V2X communication being mapped in afirst symbol in a first slot of a subframe, the second DM-RS for V2Xcommunication being mapped in a second symbol in the first slot of thesubframe, and generate a third DM-RS for V2X communication and a fourthDM-RS for V2X communication, the third DM-RS for V2X communication beingmapped in a first symbol in a second slot of the subframe, the fourthDM-RS for V2X communication being mapped in a second symbol in thesecond slot of the subframe. The mapping processes may be performed bythe processor.

The processor may control a wireless transceiver to transmit the firstDM-RS for V2X communication, the second DM-RS for V2X communication, thethird DM-RS for V2X communication, and the fourth DM-RS for V2Xcommunication to another device through a V2X communication. If agroup-hopping is enabled, the first DM-RS for V2X communication may begenerated based on a first group-hopping and the second DM-RS for V2Xcommunication may be generated based on a second group-hopping.

The first group-hopping may be associated with a first equation,(Σ_(i=0) ⁷c(16n_(ss) ^(PSSCH)+i)·2^(i))mod30, and the secondgroup-hopping may be associated with a second equation, (Σ_(i=0)⁷c(16n_(ss) ^(PSSCH)+8+i)·2^(i))mod30. Here, c(x) for the first equationand the second equation denotes a pseudo-random sequence that is definedas a length-31 Gold sequence and n_(ss) ^(PSSCH) denotes a current slotnumber in a subframe pool for a sidelink. n_(ss) ^(PSSCH)=k for thefirst slot of the subframe and n_(ss) ^(PSSCH)=k+1 for the second slotof the subframe, where k is a non-negative integer. The number k may beone of 0, 2, 4, . . . , 18 of ten subframes arranged in the subframepool.

The processor may apply first orthogonal sequence [+1 +1 +1 +1] orsecond orthogonal sequence [+1 −1 +1 −1] in association with the first,second, third, and fourth DM-RSs for V2X communication. The firstorthogonal sequence [+1 +1 +1 +1] may be configured to be applied when amodulo-2 operation of an identifier is equal to zero, and the secondorthogonal sequence [+1 −1 +1 −1] may be configured to be applied whenthe modulo-2 operation of the identifier is equal to one.

According to one or more exemplary embodiments, each of the first slotand the second slot consists of seven symbols, respectively (normalcyclic prefix). As shown in the part (b) of FIG. 5, when the first slotprecedes the second slot in a time axis, the first symbol in the firstslot is symbol #2 and the second symbol in the first slot is symbol #5if the seven symbols in the first slot are arranged from symbol #0 tosymbol #6, and the first symbol in the second slot is symbol #1 and thesecond symbol in the second slot is symbol #4 if the seven symbols inthe second slot are arranged from symbol #0 to symbol #6.

According to one or more exemplary embodiments, an apparatus and methodfor receiving Demodulation-Reference Signal (DM-RS) configured forVehicle-to-everything (V2X) communication are provided. An apparatus maybe equipped in a vehicle, such as a car, motorcycle, and the like.However, the apparatus may be equipped in other devices configured for aV2X communication.

The apparatus may include a processor, a memory, and a wirelesstransceiver including an RF module and an antenna. The processor mayreceive and decode a first DM-RS for V2X communication and a secondDM-RS for V2X communication, the first DM-RS for V2X communication beingmapped in a first symbol in a first slot of a subframe, the second DM-RSfor V2X communication being mapped in a second symbol in the first slotof the subframe, and receive and decode a third DM-RS for V2Xcommunication and a fourth DM-RS for V2X communication, the third DM-RSfor V2X communication being mapped in a first symbol in a second slot ofthe subframe, the fourth DM-RS for V2X communication being mapped in asecond symbol in the second slot of the subframe.

The processor may generate a first DM-RS for comparison, a second DM-RSfor comparison, a third DM-RS for comparison, and a fourth DM-RS forcomparison. The generation may be performed based on the equationsdescribed above. The processor may compare the first DM-RS for V2Xcommunication with the first DM-RS for comparison, compare the secondDM-RS for V2X communication with the second DM-RS for comparison,compare the third DM-RS for V2X communication with the third DM-RS forcomparison, and compare the fourth DM-RS for V2X communication with thefourth DM-RS for comparison. The first DM-RS for comparison may begenerated based on the first group-hopping, and the second DM-RS forcomparison may be generated based on the second group-hopping.

While the present invention has been shown and described in connectionwith the embodiments, it will be apparent to those skilled in the artthat modifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.Thus, the present invention is not limited to the foregoing embodimentsand may include all the embodiments within the scope of the appendedclaims. For example, various exemplary embodiments have been describedwith respect to 3GPP LTE or LTE-A systems; however, aspects of theillustrated embodiments may be applied to other mobile communicationsystems.

What is claimed is:
 1. A wireless user device comprising: a wirelesstransceiver comprising an antenna and configured to receive one or moremessages comprising one or more parameters associated withVehicle-to-everything (V2X) communication; and one or more processorsconfigured to: determine, based on a first group-hopping associated witha first time resource, a first Demodulation-Reference Signal (DM-RS) forV2X communication, and determine, based on a second group-hoppingassociated with the first time resource and with an offset, a secondDM-RS for V2X communication, wherein the first group-hopping and thesecond group-hopping apply different inputs in a pseudo-random sequence;map the first DM-RS for V2X communication in a first symbol in the firsttime resource, and map the second DM-RS for V2X communication in asecond symbol in the time resource; determine, based on a thirdgroup-hopping associated with a second time resource, a third DM-RS forV2X communication, and determine, based on a fourth group-hoppingassociated with the second time resource and with an offset, a fourthDM-RS for V2X communication, wherein the third group-hopping and thefourth group-hopping apply different inputs in the pseudo-randomsequence; and map the third DM-RS for V2X communication in a firstsymbol in the second time resource, and map the fourth DM-RS for V2Xcommunication in a second symbol in the second time resource, whereinthe wireless transceiver transmits the mapped first DM-RS for V2Xcommunication, the mapped second DM-RS for V2X communication, the mappedthird DM-RS for V2X communication, and the mapped fourth DM-RS for V2Xcommunication.
 2. The wireless user device of claim 1, wherein the firstgroup-hopping and the third group-hopping are associated with (Σ_(i=0)⁷c(16n_(ss) ^(PSSCH)+i)·2^(i))mod30, and wherein the secondgroup-hopping and the fourth group-hopping are associated with (Σ_(i=0)⁷c(16n_(ss) ^(PSSCH)+8+i)·2^(i))mod30, where c(x) denotes thepseudo-random sequence that is defined as a length-31 Gold sequence andn_(ss) ^(PSSCH) denotes a current slot number in a subframe pool for asidelink, wherein the first time resource is a first slot of a subframe,and wherein the second time resource is a second slot of the subframe.3. The wireless user device of claim 2, wherein n_(ss) ^(PSSCH)=k forthe first slot of the subframe and n_(ss) ^(PSSCH)=k+1 for the secondslot of the subframe, where k is a non-negative integer.
 4. The wirelessuser device of claim 1, wherein the wireless transceiver is configuredto transmit, using first orthogonal sequence [+1 +1 +1 +1] or secondorthogonal sequence [+1 −1 +1 −1], the first, second, third, and fourthDM-RSs for V2X communication.
 5. The wireless user device of claim 4,wherein the one or more processors is configured to use the firstorthogonal sequence [+1 +1 +1 +1] based on a modulo-2 operation of anidentifier being equal to zero, or wherein the one or more processors isconfigured to use the second orthogonal sequence [+1 −1 +1 −1] based ona modulo-2 operation of the identifier being equal to one.
 6. Thewireless user device of claim 1, wherein the one or more processors isconfigured to: determine to transmit, to a target wireless user device,a V2X data channel; and determine, for mapping the first, second, third,and fourth DM-RSs, a plurality of symbols in the first time resource anda plurality of symbols in the second time resource, wherein the first,second, third, and fourth DM-RSs are associated with the V2X datachannel.
 7. The wireless user device of claim 1, wherein the one or moreprocessors is configured to: determine whether to enable a group-hoppingfor DM-RSs associated with a V2X data channel.
 8. The wireless userdevice of claim 1, wherein each of the first time resource and thesecond time resource consists of seven symbols, respectively, whereinthe first time resource precedes the second time resource in a timeaxis, wherein the first symbol in the first time resource is symbol #2and the second symbol in the first time resource is symbol #5, the sevensymbols in the first time resource being arranged from symbol #0 tosymbol #6, and wherein the first symbol in the second time resource issymbol #1 and the second symbol in the second time resource is symbol#4, the seven symbols in the second time resource being arranged fromsymbol #0 to symbol #6.
 9. A system comprising: a base stationconfigured to transmit one or more messages comprising one or moreparameters associated with Vehicle-to-everything (V2X) communication;and a wireless user device comprising: a wireless transceiver comprisingan antenna and configured to receive, from the base station, the one ormore messages; and one or more processors configured to: determine,based on a first group-hopping associated with a first time resource, afirst Demodulation-Reference Signal (DM-RS) for V2X communication, anddetermine, based on a second group-hopping associated with the firsttime resource and with an offset, a second DM-RS for V2X communication,wherein the first group-hopping and the second group-hopping applydifferent inputs in a pseudo-random sequence; map the first DM-RS forV2X communication in a first symbol in the first time resource, and mapthe second DM-RS for V2X communication in a second symbol in the timeresource; determine, based on a third group-hopping associated with asecond time resource, a third DM-RS for V2X communication, anddetermine, based on a fourth group-hopping associated with the secondtime resource and with an offset, a fourth DM-RS for V2X communication,wherein the third group-hopping and the fourth group-hopping applydifferent inputs in the pseudo-random sequence; and map the third DM-RSfor V2X communication in a first symbol in the second time resource, andmap the fourth DM-RS for V2X communication in a second symbol in thesecond time resource, wherein the wireless transceiver transmits themapped first DM-RS for V2X communication, the mapped second DM-RS forV2X communication, the mapped third DM-RS for V2X communication, and themapped fourth DM-RS for V2X communication.
 10. The system of claim 9,wherein the first group-hopping and the third group-hopping areassociated with (Σ_(i=0) ⁷c(16n_(ss) ^(PSSCH)+i)·2^(i))mod30, andwherein the second group-hopping and the fourth group-hopping areassociated with (Σ_(i=0) ⁷c(16n_(ss) ^(PSSCH)+8+i)·2^(i))mod30, wherec(x) denotes the pseudo-random sequence that is defined as a length-31Gold sequence and n_(ss) ^(PSSCH) denotes a current slot number in asubframe pool for a sidelink, wherein the first time resource is a firstslot of a subframe, and wherein the second time resource is a secondslot of the subframe.
 11. The system of claim 10, wherein n_(ss)^(PSSCH)=k for the first slot of the subframe and n_(ss) ^(PSSCH)=k+1for the second slot of the subframe, where k is a non-negative integer.12. The system of claim 9, wherein the wireless transceiver isconfigured to transmit, using first orthogonal sequence [+1 +1 +1 +1] orsecond orthogonal sequence [+1 −1 +1 −1], the first, second, third, andfourth DM-RSs for V2X communication.
 13. The system of claim 12, whereinthe one or more processors is configured to use the first orthogonalsequence [+1 +1 +1 +1] based on a modulo-2 operation of an identifierbeing equal to zero, or wherein the one or more processors is configuredto use the second orthogonal sequence [+1 −1 +1 −1] based on a modulo-2operation of the identifier being equal to one.
 14. The system of claim9, wherein the one or more processors is configured to: determine totransmit, to a target wireless user device, a V2X data channel; anddetermine, for mapping the first, second, third, and fourth DM-RSs, aplurality of symbols in the first time resource and a plurality ofsymbols in the second time resource, wherein the first, second, third,and fourth DM-RSs are associated with the V2X data channel.
 15. Thesystem of claim 9, wherein the one or more processors is configured to:determine whether to enable a group-hopping for DM-RSs associated with aV2X data channel.
 16. The system of claim 9, wherein each of the firsttime resource and the second time resource consists of seven symbols,respectively, wherein the first time resource precedes the second timeresource in a time axis, wherein the first symbol in the first timeresource is symbol #2 and the second symbol in the first time resourceis symbol #5, the seven symbols in the first time resource beingarranged from symbol #0 to symbol #6, and wherein the first symbol inthe second time resource is symbol #1 and the second symbol in thesecond time resource is symbol #4, the seven symbols in the second timeresource being arranged from symbol #0 to symbol #6.
 17. A methodcomprising: receiving, by a wireless transceiver of a wireless userdevice, one or more messages comprising one or more parametersassociated with Vehicle-to-everything (V2X) communication; determining,by the wireless user device and based on a first group-hoppingassociated with a first time resource, a first Demodulation-ReferenceSignal (DM-RS) for V2X communication, and determining, based on a secondgroup-hopping associated with the first time resource and with anoffset, a second DM-RS for V2X communication, wherein the firstgroup-hopping and the second group-hopping apply different inputs in apseudo-random sequence; mapping the first DM-RS for V2X communication ina first symbol in the first time resource, and mapping the second DM-RSfor V2X communication in a second symbol in the time resource;determining, based on a third group-hopping associated with a secondtime resource, a third DM-RS for V2X communication, and determining,based on a fourth group-hopping associated with the second time resourceand with an offset, a fourth DM-RS for V2X communication, wherein thethird group-hopping and the fourth group-hopping apply different inputsin the pseudo-random sequence; mapping the third DM-RS for V2Xcommunication in a first symbol in the second time resource, and mappingthe fourth DM-RS for V2X communication in a second symbol in the secondtime resource; and transmitting the mapped first DM-RS for V2Xcommunication, the mapped second DM-RS for V2X communication, the mappedthird DM-RS for V2X communication, and the mapped fourth DM-RS for V2Xcommunication.
 18. The method of claim 17, wherein the firstgroup-hopping and the third group-hopping are associated with (Σ_(i=0)⁷c(16n_(ss) ^(PSSCH)+i)·2^(i))mod30, and wherein the secondgroup-hopping and the fourth group-hopping are associated with (Σ_(i=0)⁷c(16n_(ss) ^(PSSCH)+8+i)·2^(i))mod30, where c(x) denotes thepseudo-random sequence that is defined as a length-31 Gold sequence andn_(ss) ^(PSSCH) denotes a current slot number in a subframe pool for asidelink, wherein the first time resource is a first slot of a subframe,and wherein the second time resource is a second slot of the subframe.19. The method of claim 18, wherein n_(ss) ^(PSSCH)=k for the first slotof the subframe and n_(ss) ^(PSSCH)=k+1 for the second slot of thesubframe, where k is a non-negative integer.
 20. The method of claim 17,wherein the transmitting comprises transmitting, using first orthogonalsequence [+1 +1 +1 +1] or second orthogonal sequence [+1 −1 +1 −1], thefirst, second, third, and fourth DM-RSs for V2X communication.
 21. Themethod of claim 20, wherein the first orthogonal sequence [+1 +1 +1 +1]is used based on a modulo-2 operation of an identifier being equal tozero, or wherein the second orthogonal sequence [+1 −1 +1 −1] is usedbased on a modulo-2 operation of the identifier being equal to one. 22.The method of claim 17, further comprising: determining to transmit, toa target wireless user device, a V2X data channel; and determining, formapping the first, second, third, and fourth DM-RSs, a plurality ofsymbols in the first time resource and a plurality of symbols in thesecond time resource, wherein the first, second, third, and fourthDM-RSs are associated with the V2X data channel.
 23. The method of claim17, further comprising: determining whether to enable a group-hoppingfor DM-RSs associated with a V2X data channel.
 24. The method of claim17, wherein each of the first time resource and the second time resourceconsists of seven symbols, respectively, wherein the first time resourceprecedes the second time resource in a time axis, wherein the firstsymbol in the first time resource is symbol #2 and the second symbol inthe first time resource is symbol #5, the seven symbols in the firsttime resource being arranged from symbol #0 to symbol #6, and whereinthe first symbol in the second time resource is symbol #1 and the secondsymbol in the second time resource is symbol #4, the seven symbols inthe second time resource being arranged from symbol #0 to symbol #6.